C5 Vette 4L60E No 2-3 Shift @ WOT

[jrs_c5]

Hello everyone, I'm new here. I bought a C5 vette and it will not shift from 2-3 at WOT. It goes right up to the rev limiter, it never even tries to shift, until I let off the gas. Also when cruising at about 55-65mph TCC lock up goes on and off untill it causes a CEL. P1870. I DO NOT have an HP Tuner, but I have been reading many posts here and people with the tuner tend to have the same problems. Is there any way to know if the previous owner changed the shift points or something on the car with out me having a tuner? Or is there someone in my area who has a tuner and could just plug it in and show me if it was tuned before? I just want to know, you don't have to tune my car, I understand the tuner costs money. I'm willing to pay someone just to know if my car was tuned before.

Or could it be related to the VSS http://www.hptuners.com/forum/showthread.php?p=152363 ? But if it was the VSS, wouldn't the speedo quit working too?

I live in Bradenton, Fl 34203

Thanks for any help on this issue!
Juan