I had my 03 996tt for about two years now. It’s alway has a slightly high idle, 1050-1100rpm. The previous owner said that’s because the tune. I drive 4 miles one way to work with the highest speed limit is 45mph, so the high idle never bothered me.
About two months ago I took a friend for a ride, so we did a quick pull thru the middle of 4th gear. I felt something popped and the idle is now around 1200rpm with very slow return to 1100rpm. So I knew it a vacuum leak somewhere.

I got some free time today so I decided to tackle the Porsche. I’ve always dreaded working on the Porsche but something has to be done. Took off the Y pipe, the little vacuum hose had a tear in it. Way too easy right? Plus it’s infront of the tb so that’s not it. Took the TB off, low and behold, two vacuum hoses are not connected to anything. Can’t quite access it with the cramp engine bay, I took both the BOV off and still not enough space. Time for drastic measures, lower the engine by unscrew the engine mount as far as I can. That’s work!! I must had zip tie at least twenty connections in there. Bolted everything back, went for a test drive, my car has never been this responsive. Best part, it idles at around 900rpm now. I’m falling in love with this car all over again. I can not believe what a vacuum, or three, leak can literally ruin a car like this. I can now check my oil again, it’s perfectly full btw.

Anyway, thank you for reading this long post, but I felt like I need to write it. And this diagram on post #15 should be on every 996tt owner tool box
https://rennlist.com/forums/996-turb...ng-it-out.html

until next time

Good work. I hope you hooked a compressor up and pressurized the outlet side of the turbos to check it. Plenty of DIYs describing this.