I've had this happen before and luckly knew exactly what it was the first time it did it, but I thought I would share this information for everyone else just incase you run into this problem.

I was tuning on a 99 Camaro today that had a stock 4L60E and stock longblock LS1 with a 224 cam and a crap typhoon intake and throttle body, when we would go to do a WOT pull it would shift out of 1st gear and just bog down really hard. At first you will think the trans is screwed up but what it actually was was the throttle body! The throttle body was opening too far and the PCM was seeing 5.00 volts and just by guestimating the PCM freaks out and it senses that it's not WOT and reverts to a different TPS % that is really low and causes the transmission parameters to read lower in the table and shift early. It was shifting from high RPM in 1st straight into 3rd gear it seemed like.

So luckly the throttle body had a WOT set screw as well so I could adjust it to where it wouldn't open as far. I got it to where it was readying around 4.67 volts to be safe and prevent a TPS high voltage code and freaking out.

This info may help someone that is having fits with there car out. Thought I'd share.

BTW... when are we going to get a Table in the diagnostic tab to allow us to adjust the voltage that would throw an error? Reason I ask is cause my Fast90 does this all the time and I just disabled the code all together on it to keep it acting right.