what is going on?

[silviagod]

Can anyone offer advice please.
My Silvia is misbehaving, it drives well but is damned uneven on idle. I have tried different fuel pumps, distributors, fuel pressure regulators, air-flow sensors, ECU's and the damn thing still does the same. It is perfect from cold until it warms up and in order to keep the damn thing running I am up to 2.5 bar on the fuel pressure. If I allow more air to get in it runs rich as hell because I forgot to put the dump valve back on and it ran perfect but very fast. I also tried blocking off the dump valve to eliminate it from the equation. I suspected No." injector at one time and replaced it to no effect and the spark plugs are new. If I unplug the air-flow sensor it runs slightly rich and idles perfect. I tested the wiring from the air-flow sensor to the ECU and that is ok, the water temp sensor is working fine and I have a healthy spark. I first became aware of the problem when the temperature took a dive and we had a sharp frost and the ECU codes are showing no faults.

Please please please can you offer any suggestions where to look next? The only thing I haven't checked are the valve clearances and a dry compression test on a warm engine is giving 150psi on all cylinders.