jonbill

you've either been incredibly unlucky or its not the diff. anything unusual about the suspension or gearbox setup? whats the noise like coasting out of gear? in gear with the clutch in?

This thing. It can be screwed in and out a bit to adjust height. (photo borrowed from jdmcarparts.com)

if you can get it low enough at the front but its too high at the bulkhead, the height can be adjusted by screwing in the catch bolt in the bonnet. if that doesnt make any difference, check if the bonnet is resting on the rad core support at the front. if it is, you'll have to take the bumper off z loosen all the wing bolts and raise it a bit and start again.

cold start isn't what happens when its cold outside and you start your car. ANY outside temperature is a lot colder than the running temperature of the engine, and it needs fuel and timing adjustments while it warms up. so suspect a temp sensor somewhere.

I don't think you're engine is running lean.

Yes, just lowered. Its a diesel block, 20mm taller, and I wanted it to still fit under my strut brace.

Fwiw, I lowered my engine 20mm and had to grind a little off the oil pan edge and rack mount. so 2" lowering would need some work.

I think the LD28 oil pump is the same as the NA petrol oil pump. the LD28 water pump is higher capacity than NA petrol and the petrol Turbo oil pump is higher capacity than NA petrol. you can buy the Hitachi turbo zx oil pump from rockauto.

the hose is probably for the MAP sensor in the MS. it measures the air pressure in the manifold. (high with the throttle shut , low with it wide open). It needs to connect to the inlet manifold between throttle and engine. the place you bought it must have some instructions.

The diagram shows the injectors have +12v at all times I think; doesn't go through the switch. So: it will idle on 5, but if you try to rev it higher, it dies. correct? But, if you ground the 6th,through your test light, it will rev. correct? as @NewZed said, its probably bad earths from the ECU.

so it runs with any 5 of 6 injectors plugged in and any 1 of 6 disconnected? or is it a specific one that has to be disconnected?

The epoxy putty fell off during the run in, but it didn't leak 🙃 I've put another lump on now, mainly for luck!

Progress is delayed. I hadn't noticed the bead on the gasket is just outside the block where the coolant bypass is on a petrol block, and I had a leak when I assembled it. I've built the block out with a spot of epoxy putty to give the bead something to sit on. No idea how long it will hold, but tomorrow should be first start.

what cut out switch is it? maybe its got some diodes (or?) that affect the potential of the ground. or maybe the connection just isn't good.