[Joeaksa]

Do you have the maintenance records from the previous owner? 90k is about the limit on a oxygen sensor and would be nice to know if its been replaced. You can replace them yourself if you are a bit mechanical. Its located on the exhaust pipe under the left rear wheel well. Look for something that looks like a sparkplug screwed into the exhaust pipe with wires attached. Pelican sells them and I would get a "Bentley" tech manual as well.

Dave is correct about the cap. Have you checked all the vacuum hoses around the motor compartment? Several there and they can cause idle problems. How far are you from Long Island? Some good people over there and there was a thread in the last week with several people helping a new owner on LI with various issues on his car.

I had my car stutter on takeoff and could not find it. Took it to a shop and they scoped it and the distributor cap was cracked on the back side. Fixed it in 30 minutes and drives fine now...

One issue with cars that have not been driven much is white foam on the oil cap. If you do not drive the car long enough to let the oil get to operating temp you can get a white foamy deposit on the oil cap. Take the car out and drive it, get it warm and go on the highway for a bit. Then check the oil again and it should go away...

911's are different but once you get to know them there's no substitute!

Joe