choleaoum

Alright so I got my SR20DET running on my 73 510 but it won't hold idle. IACV has been cleaned, and even replaced. TPS has been calibrated and checked. Grounds have been checked for continuity and even added more grounding points with alligator clips. MAF has been changed several times. Tried checking the timing, No vacuum leaks. No loose hoses, No loose IC piping. All new gaskets for intake & exhaust manifold. PCV are hooked up. All wires have been unhooked and checked for corrosion. Temperature sensor is hooked up. It revs up fine, it's running a bit lean. Is there anything I possibly ruled out? The engine was running great before I personally removed it myself from my friends S13.

Cliffs:
- Engine was removed running by me personally and swapped into my 510.
- TPS is calibrated.
- MAF was changed twice.
- Grounds are clean and checked for continuity.
- No vacuum leaks.
- Both manifolds have new gaskets.
- PCV is hooked up.
- Engine stumbles and dies at idle but revs up great. Running lean.
- No corrosion in the wires.
- Temp sensor is hooked up.
- Cleaned IACV & even replaced it.
- ECU have been disconnected and reconnected.

Tried disconnecting IACV runs the same, disconnected the MAF and it runs whatever. Still dies. The IACV is actuating though, we disconnected and watched it.

My next step is to replace the ECU but is there anything I could have overlooked? My wiring looks great, no loose ends. Unless there's a super secret hidden ground wire somewhere.