Well I've been searching for a few months (yes i know about the search feature thanks) now for a solution to this without wanting to spend 1k ish on nistune+install+tuning and its gotten pretty bad after going from having the air filter just run directly off the maf in the engine bay, i added the Cold Air intake i fabed up this weekend which goes down next to the IC piping into the Wheel Well. i don't know if this is causing the problem or amplifying an existing problem. I also recently added the FMIC + BOV (Recirculated) this past week.
First off here's what i'm working with:
Stock Internally RB20DET
Stock ECU
Stock Turbo running 10psi
Stock Injectors and Coils that came with the car
Walbro 255lph in-tank fuel pump
FMIC w/ 2.5in piping
HKS SSVQ (Recirculated) (This BOV is giving me the compressor surge spuddering at low boost)
Custom CAI using a Cone Filter on 3in piping and Stock RB20DET MAF
APEXi N1 Catback 3in
Spec Stage 1 Clutch
Competition Lightweight Flywheel (was told this could be affecting the decel and causing the RPMs to fall too fast)
I have a Z32 MAF and Nismo FPR that i need to install, would these help? I also put some fuel injector cleaner in my last fill up thinking the injectors might be cloged but didnt help any.
Problem:
The car runs perfectly fine and pulls hard under boost. During idle it fluctuates radically between 500 and 900RPM ... tries to fall on its face like its got a big cammed v8 in it or something, it leans out during this from 14.1 to +18.0. also when i push in the clutch to stop once its warmed up, it drops the RPMs down to 5-600 and almost dies unless i heel toe the gas and brake to keep it up. when its cool it stops at around 1100, then levels off to its usual 850ish idle.
i'm aware it could be several things and i'm willing to look into them... like cleaning the AAC Valve and whatnot... just need to know where i should start. Prior to the FMIC and CAI it was running fine. Could it possibly need a tune that bad due to colder intake air? Should i change the stock spark plugs? could it be the coils going out? it doesn't misfire in boost or studder...
I figured i'd come ask you guys in AU since you have more experience with the RB20 then most of the guys here in the states.