when im dirivng the car down the street (at night of coarse) if i hit the gas the headlights go dim. if i stay on the gas the headlights stay dim. if i never get on it the lights stay bright. any ideas? i brought the car to gm and they flashed my computer and messed up my tune and all kinds of nastyness so i wanna not to that again. before i go and try and mess with it on my own i would like an idea of what could be the problem. the car has 27k miles on it. a 3.0 inch pulley stock adjuster.

 

Sounds like you need a stronger battery...or maybe just a ground kit...or maybe im way off

 

well gm replaced my alt. belt. and tentioner

 

i would assume they checked the actual alternator?

 

well they replaced the bet and tnesioner first cause they didnt want to replace te altenator... then they noticed it still didnt fix the problem so they then replaced the altenator

 

The alternator would be my first guess...cause I might be wrong, but I'm pretty sure the battery doesn't do anything when the vehicle is actually running, its all on the alternator. The battery just starts your car, and runs the accessories when the car is off.