Surging idle when driven hard
 

The last couple times I've taken the 944 out, the idle surges after I really push it (5000+rpm). It will run fine on-throttle, but after the hard driving, at idle, the revs will drop to about 300rpm, then come back to 1000, then drop to 400 or so, come back to 1000, drop to 500 or so, until it evens out.

My first thoughts were "vaccuum leak" and "TPS," but I was wondering which of these would have anything to do with the spirited driving...

I have a semi-related problem (it idles at 1300 and stays there only after warmed up and being driven hard). I'm thinking vacuum leak or TPS, too. Easiest thing first - do the search for a leak with some carb cleaner when its idling funny. This might reveal something quick.