If you still havve the original throttle linkage plate (the one the throttle and TV cable hooks up to) keep it. If not, go get one. The are around $13 at the GM parts store. I tried all the different aftermarket ones and the original was the only one that worked. It will fit the performer set (I have it on mine also). Mostly the symptoms of a mis adjusted TV cable are late or early shift points. Early shift, too much TV, and late shift too little TV. To adjust it, with engine off, have someone press the gass pedal all the way to the floor and hold it. Next, press the adjusting button on the TV cable and hold it while pushing the sleeve (the plastic portion that protrudes out from the center of the TV cable) towards the firewall until you feel it stop. This will get you very close. Release the adjusting button and then the pedal. Take it for a test drive and see how it works. If everything is okay within the tranny, you should notice a difference. With what you describe, sounds more like the valve body may have some crude in it on the 2-3 shift vale or the walls/piston are scored.
Another reason for this is during the rebuild someone has opened up the 2-3 feed hole to more than .093''. This causes the 2-4 band to be pushed off before the 3-4 clutch is applied. The fix requires a tear down of the transmission again and check that the 3-4 clutch clearance is between .025'' - .062'' and make sure 2-3 feed hole is .093'' or less (on the valve body spacer plate). Also, using a Vette servo # 093 will help to get rid of a 2-3 flair. But the 1-2 and 2-3 shift will be much firmer and this will lower the life expectancy of the tranny.
