Just ran into an old post talking about this identical problem. Runs good when cold, then skips when hot, lousy performance, etc. These guys were talking about the CRANKSHAFT POSISION SENSOR being bad, and upon replacement, the car running like a scalded dog! Here's a link to the post:

http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=trouble&Number=1209527&page=2&view=collapsed&sb=5&o=7&fpart=10&vc=1

Go to page 10 in the thread and it has a good illustration as to where it is and how to get to it. I'm going to try it myself, as I have the exact same issue with my car. I guess this is common and people end up replacing all kinds of stuff with no results.

The part is $13.50 at Autozone!

http://www.autozone.com/servlet/UiBroker?UseCase=C001&UserAction=doYMME&Parameters=Auto+Store%7C%7EREGULAR+PARTS+LOOK+UP%7C%7E00111

Mike

PS--though it didn't fix my car completely, cleaning out the throttle body with carb cleaner and a toothbrush did help a lot. Only takes about 5 mins to bear the thing and just clean it on the car. Make sure you pull fuses 4 and 11 in the fusebox by the battery to clear the computer's memory or it'll continue running crappy!