No forced induction setup should run the IAT sensor BEFORE the compressor/turbo. That is just plain faulty engineering and a recipe for disaster. The sensor needs to be post-compressor/charge cooler so the ECU gets an accurate measure of the charge temp entering the cylinders. With the sensor before the compressor, there's no way to compensate for a faulty charge cooler or heat soak.
And for the record, the MS45's IAT sensor transfer function is DIFFERENT than that of the MS41/42/43 IAT sensor. Don't think you can just replace one for the other and your problems are solved.
2001 330ci Turbo
Last edited by NickG; 11-07-2012 at 08:53 AM.