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sounds like a bad MAF, fuel supply problem or boost leak!
before throwing parts at the car like you have, especially if the car was running normally for a while when you first got it, start looking at the things that cause these issues... most people cheap out on silicone couplers and tbolt clamps. a lot times kids know will just buy cheap ass, paper thin couplers to use on the intercooler piping (or the chinese made shit the intercooler kit comes with) or those throw away screw clamps that are only good for two uses at most.
go thru your engine bay and make sure ALL of your clamps are VERY secure around your couplers. make sure ALL of your vacuum lines are healthy rubber and dont have any splits in them (especially around the nipple area). also, do yourself a favor and get some smaller zipties to clamp the vacuum hoses over the nipples.
even the slightest vacuum leak can cause HUGE issues with your SR, and again, most SR swaps these days are cheaply done and just ghetto shit! most younger guys dont take the time or the money and do things correctly! just slappy slappy, hey it runs, who cares!
if youre having a fuel supply problem, it MAY be time to replace the fuel pump... ESPECIALLY if its a walbro. walbros cannot be run below quarter of a tank of gas (especially in hot places like vegas or phoenix). walbros NEED the gas to keep them cool otherwise the motor/amplifiers in them blow and they stop working! you wind up running into fuel starvation and the motor will no longer run above 4000rpms at mid to full throttle (youll just rev bounce).
MAFs have a habbit of getting very dirty very quickly which, again, will cause major issues. Z32 or SR MAFs are known for being the bitchiest things on the planet! even if you have a small amount of dust/dirt built up on the wires, kiss your hope for a normal running motor goodbye. i clean mine using a mix of B12 carb cleaner (sprayed at the wires and applied on a q-tip) along with MAF cleaner.
when diagnosing these problems start at the point where the air enters the motor. and work from there. if your car is running lean, then you have a leak on the intake of the turbo, if its running rich, you have a leak after the turbo. if youre 100% sure you dont have a boost/vacuum leak, then move on to the MAF. if youre 100% its not the MAF, then move on to the fuel components like your fuel pressure regulator, fuel lines and fuel pump. if youre 100% sure its not the fuel components, then move onto ignition... see where im going with this?
also, one MAJOR thing you need to check is the torque on the intake manifold. get a torque wrench and make sure the nuts on the studs from the head are properly torqued to 14-15lbs AT MOST!!! minimum torque on them i believe is 13lbs. DO NOT TORQUE THEM OVER 15LBS OR YOU RUN THE RISK OF STRIPPING OUT A STUD!!! INVEST IN A TORQUE WRENCH, DO NOT GUESS ON THE TORQUE AMOUNT ON MOST COMPONENTS OR YOU WILL BREAK SHIT!!! there are 2 sets of nuts, the ones on the head and the ones on the runners going to the intake plenum.
also, reset your timing back to 15deg BTC, set your TPS voltage to .45 volts when shut, reset your idle using the IACV... having a messed up TPS will really screw with your SR as well!
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