I just did a head gasket and timing cover replacement on my 02 9-3 SE. I replaced the head gasket because of a major oil leak, not because it blew. I finally got everything back together and I'm having issues with the engine idling roughly. If I open the throttle slightly to speed the engine up, the engine stalls when I let off the throttle. I've checked all of the vacuum hoses and everything seems fine. I even tried a different ignition cassette, just in case the other one got knocked over and damaged. I also noticed that if I disconnect the positive terminal of the battery after the car is running, it idles even more roughly. I've never known an alternator to effect the way an engine runs, but I think it's important to note that the oil leak resulted in the alternator getting thoroughly covered in oil. While I had it off the car, I cleaned it in a parts washer to get the oil out of it and then sprayed it out with an entire can of contact cleaner. It let it sit for a week before I reinstalled it. I'm sure it was dry. Could the alternator cause rough idling? If not, what could cause this? I wasn't having an issue with this before I did all of this work to the engine.