Did you use an aftermarket cable?
I used one once that couldn't pull all the way out and it only "felt" like it was at full pull but it wasn't. Did you check if your gas pedal is pulling back the throttle back all the way? If you drop the pan, you can be 100% sure, if when the throttle is wide open by checking that the bellcrank is plunging the throttle valve in all the way. This is how I discovered my problem.
Shift points can be adjusted by picking up a govenor calibration kit. It comes with springs and weights to get the shifts where you want them to a degree.
Hopefully your tranny is not yet fried. If the PO was also driving around without the TV cable hooked up, it may be cooked already.
It doesn't take long.