ive got a 94 Z28 auto trans and when shifting from 3 to over drive hit the rev limiter but dont slip or anything what would it be

 

Unless its be altered in tuning the 3-4 shift is set to such a high level it will not happen at WOT before you hit the limiter

 

it has been tuned and has shift kit

 

Did this start happening right after the tune or was it fine before? If it started doing it right after the tune then its more than likely the tune. With electronic transmissions the shift has to be commanded just a bit earlier to prevent the car from hitting the limiter before the shift actually occurs.

 

the stock tuning will not allow a 3-4 shift at wot so if your tuner didnt change that then this would be normal