john sargent mentioned that in a previous post a while back as a possible source, but I have yet to get down and dirty and really check it out.

Why would a problem with the engine coolant temp sensor cause this intermittent problem? If the sensor is failing intermittently, does the failure to report the temp to the CPU trigger it to retard the timing? Does it respond to no signal like the engine is cold or like its hot?

I guess I moved past the coolant sensor because I figured I would see some indication of teh problem when the boost isn't engaged as well as when it is. The fact that it only appears when I'm boosting keeps pushing me towards an electronic item associated with the turbo.

Argh... well, I need to swap outthe radiator and the heater valve, so maybe I'll just do the coolant sensor at teh same time. Just to be sure, the sensor you are talking about is the one under the intake manifold, right? Not the one on over near the water pump?

thanks,
-rt