When I am on the highway at 65-75 mph and I floor it while in overdrive the car will shift into second past redline. Redline is at 5000 rpm in my car and sometimes it will downshift past 5500 rpm. I have had a TransGo Stage 1 shift kit, Corvette Servo, and .500" boost valve for 2 years on my 91 GTA without a problem until this year. My car has 119,000 km (74,000 miles on it and the tranny has never been rebuilt to my knowledge).

Last month I took the TB bolts off to replace the IAC housing and I left the cables attached to the throttle body. I also replaced the busted stock tranny mount with a Prothane one. I have adjusted the TV cable on a few occasions as per the instructions in the tech section but I still have the problem. Also, this does not happen everytime I floor it on the highway. Does anyone have any ideas on what could be the problem? Thanks.

Does anyone have any ideas as to what could be wrong?