My last post I said I'd talk to Simon at Simons Services. Instead I've just come off the phone to another (ex) Landrover specialist that I've done a lot of work for in the past. Chris used to run Elland Landrovers in Halifax and before that worked at a Landrover dealership (said for every diesel they sold they'd sell about 30 petrol V8 P38s). Before that he worked for Scania and was involved in developing diesel / LPG blend systems. He's mostly involved with landscape gardening now but still does a bit with Rangerovers and has built plenty RV8s in his time. As a great coincidence he was just approaching his mate's premises while I was on the phone and I got chance to speak to his mate too, his mate is a BMW tech bloke who's very familiar with the pumps.
Chris said before the pump is messed with the engine needs to be at TDC on either number 1 or number 6 (couldn't remember) and then a pin is inserted at the side of the pump to prevent it turning. He didn't buy electronics problems other than something that might be reported due to pump timing being out. He said it's the same pump on Freelanders, Omegas and some BMWs but the electronics are different. Said that if it was running OK before when it had the leak but isn't running OK now it's obviously due to some problem the garage has caused...
His mate also didn't buy electronics problems unless the top of the pump has been changed along with the electronics which are coded. He described the same pin procedure and reckoned a lot of garages forget about timing due to being so familiar these days with common rail setups where timing doesn't matter. This guy has rebuilt a lot of these pumps and reckons a common problem when the top of the pump has been off to replace seals is that they don't seal properly when refitted due to corrosion, which can lead to air being sucked into the system unless the innards are flattened off before refitting the top of the pump. He also said that if it was running OK before when it had the leak but isn't running OK now it's obviously due to some problem the garage has caused...
Since it starts fine but engine response is poor, the 'air getting into the system' scenario Chris's mate described seems likely to me.
Agreed with Morat.