I'm struggling with some misfiring, on LPG but on petrol too. I still have the bog standard grey cables (yes OB, I've seen your jealous making red box of Magnecors) and the standard NGK plugs. Pushing some caps firm on the plugs makes it better so I guess I need a new set.

But since I have no diagnostics and wanted to know which lead it is I did some digging in my toolbox and found my old xenon timinglight and clamped the sensor to each lead, one by one to find the one that did not light up, that is lead #8 and #4, not all the time but now and then. I also noticed that not all the leads flash in the 'double tempo' (wasted spark) but in the normal single tempo, does this mean that the coils are on their way out and what leads should I buy except Magnecors?

I bought a set off eBay, heavy duty, fitted well, and no problems, in fact they're doing great, when I saw the price of magnacores I nearly feel over, think were getting the pee takien out of us,,

I remember reading somewhere when I first got involved in wasted spark systems that the extra spark isn't so great as it isn't doing anything. On one of the very old Crypton analysers with a CRT, you could see the difference in strength between the spark that was firing and the one that wasn't. I'd suggest leads as well, I've run these http://www.island-4x4.co.uk/ignition-lead-4046-9498-intermotor-bra2001-p-3971.html (but for a Thor you'd need http://www.island-4x4.co.uk/ignition-lead-4046-9802-intermotor-hls103-bra2002-p-3972.html) and the only time I've had a problem has been when I had a hose split and they got doused in coolant. Even after they'd dried out it looked like Blackpool illuminations under the bonnet in the dark.

When I first got my Thor, it had a mismatch set of leads on it, and it soon started missing badly.

I put a set of those Intermotor ones on as well as change both coil packs for new Br*tpart ones... to be fair to them, they've done 12k miles on LPG so far and are just fine. One of the original Bosch packs had a chunk of a terminal broken off.

Thanks guys, the leadset is obvious, I was just wondering how to know when a coilpack is coming to it's end. I think it's all or nothing at all. Nothing in between.
I'll order a new leadset. I like the partname for a change :)

Coil pack insulation can breakdown, so it ends up arcing through to ground. Leads more likely though.

Fitted the Intermotor leads, what a difference! No more misfires, on petrol it is really sportish, from a trafficlight it pulls away without hesitation. On LPG it is somewhat sluggish, I think it is too lean. Will have that adjusted next week.

BTW my post about ordering the leadset was dec. 5, today UPS at the door from Island 4x4. Fast isn't it?