[Byron in Atlanta]

I replaced 3.2 engine in my '02 Boxster S with a used 3.2 from the same model year and just got it running and everything seemed in order during my first test runs. Initially, I was not pushing the engine to make sure everything was connected right and all seemed in order. This weekend I tried to open it up a little bit and discovered that the engine cuts out at about 4000 RPM. It starts spitting and sputtering and will not rev to 5000. The symptoms reminded me of bad MAF's I suffered in the past. I checked the codes and it showed a P1579 or Crankshaft Position Sensor. I cleared the code and so long as I keep the RPM's under 4000 it stays clear. The engine runs perfectly up to 4K, is highly responsive and smooth. I can hold the accelerator at 4K and it runs fine, push to 4200 and the spitting starts. If I push it hard trying to achieve 5000RPM, it throws the P1579 code.

I replaced the Crankshaft Position Sensor with the one from my blown engine. That engine was running perfectly until it threw a rod through the top of the case. Same result, spitting and sputtering at 4200 RPM. I then took out the MAF sensor and cleaned and reinstalled it. FYI, that MAF is less than a year old and probably has fewer than 5000 miles on it. It is the one that was in the car when the engine blew, and as I previously stated, it was running fine. I tired running the engine with the MAF disconnected. It still would not rev to 5000 with the spitting starting around the same RPM's. I checked the codes after that run and had P0102 (MAF input) and P1579.

A bit more info, I upgraded the IMS bearing to the LN Engineering, and upgraded the flywheel to the Aasco aluminum version with a new SPEC clutch disk and pressure plate. I am at a loss. HELP