At WOT my car wont shift out of 3rd or sometimes 2nd gear all it does is bounce of the rev limiter.It did this when I first got the car and then quit. But it just started up again. i have put an oryp with sims and a flowmaster catback since ive had it.This has really got me worried.Any help would be great.Its an a4

 

sounds like your trans is going, try flushing the transmission fluid and replacing the transmission fluid filter. The Fluid flush can be done for about 80 bux. They hook it up to your transmission cooler lines (pump in/out lines) and run till its completely flushed. The filter change is usually a couple bux more, since you have to drop the pan. Best to do the filter, then the flush.