[Wayne 962]

I still think it's probably a fuel issue. If it was a sensor or wire harness issue, then the car would have issues running hot, which you didn't seem to indicate that it did. Also, when you're changing stuff to convert to a Boxster Spec car, people tend to remove anything for weight savings - even odd panels and plastic stuff that doesn't look like it does anything, but might actually act as a heat shield.

One more thing - you can try getting one of those air-in-a-can blower things, hold it upside down, and let the cold (liquid-nitrogen type fluid) drip on the fuel lines to cool them down quickly when it's hot. This way, you can test to see if the lines are what are causing the problem. You can also try that with the crank position sensor, just for giggles too.

-Wayne