GTSBoy

Yes, but they still look concerning. Viz the circled examples..... All of this looks very unimpressive. Got some closeups?

Yes it is correct. Whenever a cylinder is on compression/firing stroke (ie, #1 in this case) then the other cylinder that is also at TDC will be on the exhaust/induction overlap.

Could be cam timing, as above, ignition timing (too retarded) or lean. All are bad.

Access it from the LHS (RHS as you're facing it from the front), from underneath, coming in sideways. It's a bastard. Probably have to remove the intake pipes.

That's called overlap. Top of exhaust stroke, beginning of induction stroke, both valves are slightly open. Exhaust is closing, inlet it opening.

What is the ECU telling you?

No, what we're saying is that the ECU is telling you there's a problem. The ECO knows more about the problem than we do. You should ask the ECU, as per Nizmo's post.

Just get the one that says it suits RB25DET.

Well.....there's your answer right there.

Absolutely. But get the wiring diagram first and look at it and understand what does what first.

Wouldn't be the sensor. It's clearly a power issue at the dash. There is no power involved in the speed sensor - it generates its own power. No. It's a wiring/connector/fuse problem. Get the wiring diagram, look for the common power or earth that could cause all these things to shit themselves at the same time.

Yes it will be fine. It's just manifold bolts. There's almost no physical difference.

Now....that's not quite true. PranK is always nice. I'm frequently grumpy.

If you google for R34 manual you will find a working link to download it.

Do you have the wiring diagram? If not, get it.

Of course it's at the switch that you touch with your fingers.

Those cams be f**ked.

Take multimeter and wiring diagram to car. Start poking around where there shouldn't be power when the switch is off.

It's still hydraulic. The pump is electric. Just the mechanical power to run the pump goes via the alternator instead of the PS pump belt.

Quoting this just to make sure it doesn't go away.

Put steering wheel back on. Put nut back on 1.5 turns. Beat the crap out of the back side of the wheel.

Won't be CAS. Unlikely to be coilpacks. More likely to be injectors. Rich from problem injectors is nowhere near as common as lean from (dirty) injectors, but it does happen. Are you all sure it's fuel and not oil?

Wiring diagram and a multimeter.

Wires are switched somewhere.

Clutch <> compressor. Compressor could be fine. Probably is. The compressor and clutch are going to be common with other cars. Take it to an auto electrician, particularly one who also does air-con regassing etc. And how can it be hard to find someone is San Fransisco to rebuild a compressor? I live in a backward city in a backward country where we all hang upside down from the ground, with a population of only a million or so people and I can probably come up with a list of 5 or 6 places that I would be able to get an air con compressor done. You have SF (pop 1M, LA (pop ~4M), the rest of California (~40M), every other city on the west coast, every city everywhere else in a country with 300 million people.