Before I start, I have had this truck for 4 years now and I have never driven another P38 so I have nothing to compare to.

Symptoms:
The engine seams gutless and lacking power when ascending long hills.
My exhaust tips are sooty.
My Gas/mileage sucks.

Things I know are wrong with the truck engine right now:
Both exhaust manifolds have cracks in them on front 2 cylinders. I did not remove heat shields yet to discover any more cracks. Very audible from inside truck under load.
Leaking oil from front of both heads.
Leaking coolant from reservoir cap.

Things replaced or fixed to try to remedy this:
Removed SAI and replaced ECU with non SAI. This was not a remedy but this shit gets in the way!
Both Cats removed and straight piped. No codes from O2 sensors after this was performed.
Replaced both ignition coils.
Replaced spark plugs.
Replaced plug wires.

Engine runs ok and idles very close to smooth. I have Nanocom Evolution but I don't know how to use the info it gives me. Any help would be great. Thx

Have you done a compression test Ray? <br>
Assuming you've got the latest firmware patch on your Nano and an SD card installed in it, It'll record in Instrument mode. Do a recording and you can then dump the .csv file onto your favourite file sharing location and we can take a look at the numbers and see what the Nano's telling you. <br>
How many miles has it got on it? <br>
If your manifolds are cracked/ leaking badly enough to be audible, that'll probably mess up your O2 levels at the lambdas. Extra O2 from leaks, seen by the sensors will cause the mixtures to be sent rich to compensate.

I have not tested compression yet.
I'm almost ready to tear into the whole thing and do the head gaskets. When it is apart I can get the manifolds repaired. If I'm digging in to do the head gaskets I figured it would be a good time to do the camshaft, lifters, pushrods etc.
The mileage is 260,000 kms approx.
I'll do a capture of the instrument mode on the way home from work and post it here.

It's a good time to do a dry/ wet comp test before you tear into the motor. Handy to know state of rings and valves before you strip so you know how deep you'll have to go into the motor.

Ok I got some readings at idle for you.
First file is O2 live readings at idle: https://www.amazon.com/clouddrive/share/kj4l39iPYSajnsAWwUu90c1iMRPoKKS17hUpvhK0ZRz?ref_=cd_ph_share_link_copy

Second file is general inputs: https://www.amazon.com/clouddrive/share/JCyOrZr8gwjZa3RnfxEFhiDAQwIoMFGZ2U4CNJygtT7?ref_=cd_ph_share_link_copy

Were the files I uploaded of any use?

Haven't had a chance to look in-depth yet. At a glance they have a significant difference from the parameters/ presentation of the GEMS data and seemed to miss vitals like RPM.

OK no problem, whenever you get a chance. If you need more info let me know please.

Just a short story ... are you sitting comfortably?

I thought to replace the camshafts on my 4.6 a couple of years ago.

I was in Dubai, and bought a camshaft (nice Piper one), followers, oil pump gear, timing kit, big end shells and thought that was it.

Workshop stripped the old engine and said that it was very worn; it could be rebored and fettled locally but would take a long time and they advised a short engine.

So, new short engine ordered and engine reassembled.

Are you still reading this?

Final bill was huge ..... they had to send out the heads for reconditioning, buy new head bolts, gaskets (at LR prices, of course) and so on.

Result was and remains very good.

Moral is?

1. It is very very easy to pour money away buying your own bits when it might be wiser to get a new unit.

2. By the time they had fettled the old heads, bought the gaskets and similar. I wish I'd bought a full engine.

I admit this was in the days when cash was more plentiful! But, the expense has now been forgotten and the engine is sound.

I hear you.
I'm not dropping a $6000 block into this truck. If I can't spruce it up to last another 60,000km then off to the bone yard it goes.

Ray is in Canada Spriggy so costs of a replacement engine are significantly higher. I can't open the csv files so can't comment on the readings but cracked exhaust manifolds will allow air to be drawn in before the O2 sensors. That will create false readings suggesting to the engine ECU that the engine is running lean. So it will pump more fuel in to get it right again which will explain the fuel consumption. Running rich will also make the engine gutless so it could be that they are the cause of all the problems.

I would suggest that the oil leaks on the heads are not from the head gaskets but from the rocker cover gaskets as there are no oilways at the front of the heads. There's waterways but not oilways. Leaking from the coolant pressure cap may be nothing more serious than a worn cap and a replacement cap is cheap enough (they are the same as 5 series BMWs making them easy to get hold of too).

Ok so I should concentrate on fixing the manifolds and go from there. Sounds like a plan.
The oil leak should not be from the rocker covers as I did those last season. It definitely looks like it comes from the front of the heads. When I did the valley gasket I also replaced the front cover gasket and the front main seal. This helped on the oil loss problem but I am still seeing it on the front of the motor.
Can the rear O2 sensors be pulled from the stream as I have got an error on those because of the lack of Cats.

Just ordered all the manifold gaskets. Hopefully the heat shields will cooperate. Who am I kidding? Lol

Update on this:
I had the manifolds welded and replaced all related gaskets. Sounds good now.
I also replaced all O2 sensors but that did not work for me unfortunately. I got the following codes on completion of work.
P0135 = Oxygen sensor heater upstream catalyst bank 1 drive cycle C - Signal too low
P0155 = Oxygen sensor heater upstream catalyst bank 2 drive cycle C - Signal too low
P0141 = Oxygen sensor heater downstream catalyst bank 1 drive cycle C - Signal too low
P0161 = Oxygen sensor heater downstream catalyst bank 2 drive cycle C - Signal too low
The sensors I bought were generic brand from Ebay. Lesson learned I guess.

I was too scared to buy anything but genuine, but we only have two sensors on the system over here....
You could try one genuine one and see if it helps before going all in?

Did you reset all the adaptive values?

I'd start by just doing the upstream ones as the downstream sensors are only to confirm the cats are working (which if they aren't there they won't be) so you may still get errors from them anyway. Faults all relate to the heater circuit rather than the sensors themselves so it may be that the generic ones have heaters with a different resistance that is causing the errors. As Morat says, did you reset the adaptive values after doing the work? What errors were you getting before, same ones or different? How does it drive now?

I reset the adaptive values once the work was complete.
I installed spark plug non-foulers on the rear sensors which cured the codes I was getting with the old sensors.
Because of all the bad info out there about which ones work with this truck the non foulers are 18mm NOT 14mm or 12mm. For the one on the North American driver side I got a 90 degree elbow one from amazon as it is too close to the prop shaft for my liking.
None of the current codes were shown before fitting the new sensors.
The truck drives better but with four sensors giving errors it is probably running very rich right now.
I have ordered new genuine Bosch sensors.
Bosch 15630 for downstream.
Bosch 15184 for upstream.

New Bosch sensors fitted. Reset adaptive values and now have the following codes:
P0135 = Oxygen sensor heater upstream catalyst bank 1 drive cycle C - Signal too low
P0155 = Oxygen sensor heater upstream catalyst bank 2 drive cycle C - Signal too low
P0141 = Oxygen sensor heater downstream catalyst bank 1 drive cycle C - Signal too low
P0161 = Oxygen sensor heater downstream catalyst bank 2 drive cycle C - Signal too low
P0134 = O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)
P1000 = Lambda Heater Upstream catalyst bank 2 Drive cycle C , signal missing

Really random thought... do you need to complete 'Drive Cycle C' for it to be happy?

From RAVE's section on OBD etc:

--> Drive cycle C:

1. Switch ignition on for 30 seconds.
2. Ensure engine coolant temperature is less than 60°C (140°F).
3. Start the engine and allow to idle for 2 minutes.
4. Perform 2 light accelerations (0 to 35 mph (0 to 60 km/h) with light pedal pressure).
5. Perform 2 medium accelerations (0 to 45 mph (0 to 70 km/h) with moderate pedal pressure).
6. Perform 2 hard accelerations (0 to 55 mph (0 to 90 km/h) with heavy pedal pressure).
7. Cruise at 60 mph (100 km/h) for 8 minutes.
8. Cruise at 50 mph (80 km/h) for 3 minutes.
9. Allow engine to idle for 3 minutes.
10. Connect TestBook and with the engine still running, check for fault codes.

NOTE: The following areas have an associated readiness test which must be flagged as complete,
before a problem resolution can be verified:
• catalytic converter fault;
• Evaporative loss system fault;
•HO2 sensor fault;
•HO2 sensor heater fault.

I wonder if you need to find a bit of road that you can do that drive cycle on and see if it will then reset the codes itself...

Given all the heater faults, have you checked the heater supply is actually live and working?

Another thing to check is compare the heater resistance with the original lambdas.

I recently bought a new bosch lambda sensor for my track car. Installed it and up popped the heater fault code. Was a bit pissed off, thinking the new sensor was fake or faulty, even though it all looked right. Measured the heater resistance, and the new one was something like 9ohms and the orignal one was 4ohms, thus the new heater was drawing less power than the ECU expected and created the fault code.

Looking at the dark side, it turns out it was a faulty engine ECU......