hey i have a 94 3.4l engine thats loosing power and i would like to upgrade motors. i was wondering what the biggest motor i could put in the car without having to change the computer?

 

AFAIK, the computer will need to be upgraded, see:
http://en.wikipedia.org/wiki/GM_60-D...ne#3.4L.2F3400

 

3.4 would be the answer. that is unless you want to go carbed. not sure why you're worried bout the PCM, as a bigger engine would entail alot more than just that...

 

It may be possible to switch engines, computers, and wiring harnesses all at once, but like 02StanGT said, a bigger engine would entail a lot more. The easiest would be 3.4-3.4 swap, but in that case you would just be better off just fixing whatever's wrong with the one you already have. Just be sure to do your homework. Believe me, you're better off if you know exactly what all needs to be done before you start.