[Porsche944]

Hey no problem!

I have my doubts about a heat related vacuum leak, but it is still a possibility.

A high idle when cold tells me that someone "tweaked" something to get the engine to idle smoothly, which usually indicates that something was interfering with cold idle engichment. Under those conditions I would expect the hot idle and cold idle to be different, and in this case the difference may be just enough to put the engine in an over run condition, causing the idle to hunt.

While you have the throttle body out make sure you clean both vacuum ports. The front port controls the evaporative emissions purge valves, and the rear port supplies vacuum to the FPR, fuel damper and one of the emissions purge valves.

When the engine is at idle the front port will have 0" of vacuum, and the rear port should have between 14" and 18" of vacuum. The only time the front port has any vacuum (about 5" on both of my cars) is when the throttle plate is just starting to open. This momentary vacuum is enough to operate the purge valves and purge the evaporative system.

Since the rear port supplies vacuum to the FPR, a low vacuum will cause a higher than normal fuel pressure which can contirbute to idle and fuel mileage problems.