i have an 03 silverado w/ a 4.3l v6

had flowmaster 40 series exhaust put on at local shop
single muffler wit dual exit pipes

been about a year since i had it installed

recently ive noticed that when running about 50mph and 30-40mph the engine will rev up but not change gears. itll only a small jump but its noticable. its like its searching for the right gear.

any idea what could be causing this.

we think its a transmission problem caused by excessive burnouts

its because its a 4L60E.... its a crappy trasmission