Check Engine Light?!?!?!?!?!

Today it was like 5 degrees (f) and I was late so i had to book it down the highway at like 85mph for about 25 minutes straight. I have a 1996 A4 Quattro 2.8L 12v. Yes the 2.8 - a piece of crap but it's my car and I need it to survive. Anyways, I got off the highway and all was good, but when I pulled to the next stop light about 2 miles down the road, I stopped and my engine started to rev to 1500 rpms and it was a very rough idle. It then after about 3 or 4 seconds went down to about 200 - 300 rpms and it felt like it was gonna stall. I drove carefully to work and it was still idling about 300 rpms. I shut if off let it sit and turned it back on and it seems to idle ok but the engine light is still on. WHAT THE HECK HAPPENED?? ALSO! it was shifting REALLY hard after the first incident. Every time I released the clutch pedal, It seemed to catch really quick. There was no smooth transition between the gears. I'm bringin it to the shop but was hoping somebody might have some suggestions before I do. Sorry for long thread but I need the help. Thanks

..take it to your mechanic and have him scan it and see what codes its throwing...

it might be the thermostat...my check engine light came on a few weeks ago and that was the problem...im guessing because it was so cold and i didnt let it warm up enough...and remember it is eight years old...not actually a new car...so you may not want to drive it so hard in the cold

yea my car also shift hard in cold weather