bradc,
Welcome to Pelican, you will find a lot of help here
Very nice 911, welcome to the joy of Porsche ownership.
Drive carefully.
First, is there any relationship between operating the clutch and the idle?
High, variable idle can be one or more of several things.
A vacuum leak, something amiss with the Warm-Up Regulator (WUR), something amiss with the Auxiliary Air Regulator (AAR) per Tom's advice and other.
Clearly it is temperature sensitive.
Modify your start-up and driving:
Shift to neutral.
Start the car.
Let the clutch out.
Put on your seat belt.
Immediately drive off.
Give full throttle but keep the revs below about 4000 until you have oil temperature.
Once warm, find some excuse to give full throttle and pull (preferably uphill) to 6000 at least once.
The purposes are to let the engine & transmission oil circulate while you put on your belt.
Second is to get the engine warmed up as fast as possible after starting.
The engine doesn’t warm-up well sitting at idle.
The engine likes some full throttle pulls to keep things clean (and the catalytic converter functioning).
(
Yes officer, it is part of maintaining my emissions system. )
See if this changes your high-idle issue (probably not).
With the engine at whatever idle, grab the air filter assembly and move it about with reasonable force.
Does the idle change (up or down)?
Again, WELCOME.
Best,
Grady