My car is a 1986 Z-28, I replaced the stock 305 TPI with a race built 10.5 : 1 compresion over bored 350 making it a 355cid TPI using the same intake with some machining and honing done to it so it would breath better. Before I had the engine done I instaled headers and a full exaughst with bigger pipes, also had a 410 rear instaled along with a race built transmition, and I am also running a NOS Nitrous system.......It has just been painted Candy Apple Red and got a bran new interior.....It looks great and makes alot of power....my problem is at wide open throttle the car dosen't shift when it should unless I come off the throttle a tiny bit.....
Could this be a problem with the throttle position sensor or Vehicle speed sensor?
ANY HELP OR SUGGESTIONS WOULD BE GREATLY APPRECIATED!!!

 

Im going to assume that you have the 700R4 since you never actually told us what trans is in the car. Check your TV cable adjustment and be sure the fluid is topped off and in good shape, first.

 

My car does the same thing and from my searches it looks like the governor gear becomes stripped on the 700R4. I don't really know automatics so I am not sure if the same problem can happen in the TH transmissions. You might try a little searching around on the forum.