Not to hijack the post, I just didn't want to start a new thread, but I have similar problem.
This is my first Boxster, I had it for about 8 months now.
I had the oil changed at the dealership not long ago (400 miles since the change), but about a week ago I noticed a short puff of blue smoke on a cold start. It's been doing that now at every cold start for about 5 seconds.
As soon as I saw the smoke I checked the oil level and it was more than the norm. I drained about 3/4 of a quart before reaching the optimum oil level. Besides that, while I was at a stop light the car felt rough on idle just like Highlow described 1... " the rpms go back and forth from about 600-800". And I've also experienced 3. with the troubled start.
My Boxster has 63k miles on it, at 62k+ I've changed the air filter, fuel filter, spark plugs, and cleaned the maf sensor + oil change/filter at the dealership. The throttle is really smooth and the car feels great, but that rough idling freaks me out.
From what I've read here on the forum and on the net, I might as well change the AOS.
But could the oil overfill have something to do with it? I will have a talk with the service manager at the dealership..