1000-1500rpm surge

[DiamondStarCar]

I just got a 1993 Talon Tsi AWD last saturday and I am very happy with it. However, I noticed today it started doing the common 1000-1500rpm surge back and forth. I had this problem on my last fwd and never actually fixed the problem...just kind of made it better with the BISS and a tune-up. This one doesn't do it all the time but it does it enough to be very annoying. When I turn on my a/c the idle drops to a steady 1000rpms and stays nicely without surge. I've noticed that it usually does it early in the day...although I live in texas and it is still very hot, therefore I dont think the temp. is the problem. Also, when I bought the car, there was no change in the rpm pattern, then I changed the oil yesterday (castrol 10w-30) and this morning its my old talon nightmare all over. I know there are some bright dsm minds who have answered this question 15,000 times before so please help me. The engine has 95k and is still in great shape. I was so excited about this finally being my "good" dsm and now this. Please help.
-Chris

 

[DiamondStarCar]

Ok, the idle problem is temp. fixed. I came home and adjusted the idle screw and sure enough, the surge was traded for a 1400rpm idle. That's right between 1400 and 1500rpm for the idle. Is that right? What do others' idle at to prevent this surge? Also, am I going to have to keep adjusting this screw because it is somehow winding itself out under the pressure...or vibrations? Would I maybe need a new o-ring for the BISS? Sorry to fire off so many questions. Please continue to post other permanent ways to fix this crazy surge. Thanks in advance.