1999 V6 Camaro

1999 chevy camaro 155,000.
One day last week I was rushing, so I decided to gun my car to pass this slow driver, then all of a sudden my car starts to stall, and hesitates a lot. It seemed like it didnt want to pass 40-45mph. I pulled over and cut my car off praying that its not my transmission. I started it back up and it drove fine, then I pulled on this parking lot and it died. I took it home. The next day it drove cool for like the first two minutes then its stared to hestate and stall the first (15mph) and second (35mph) time it switched gears almost every time its changed gears around thopse sppeds it would stall and hesitate. IT DRIVES FINE ON THE HIGHWAY ONCE I GET IT PAST 55-60MPH. Iit would act like it wants to die while im sitting at the light, I say it died like twice while sitting at lights and I put it in reverse while parking and it died, but it always starts back up without a problem. Every time it died the battery gauge would get very low right before it died. I got the alternator tested cause I have subs thinking it might be an easy fix, but it was fine, so NOW IM LOST. ANY HELP WOULD BE GREATLY APPRECIATED.