I got a 2001 gmc sierra 2500 with a 6.0 vortec and I feel like it isn't getting enough power and its sucking up too much gas...I think so but I really don't know, I have seen the needle on the gas meter run to E as I hit the accelerator....not outrageously fast but I could tell the needle went down more than it was supposed too... It has a somewhat new trans. But when I hit the accelerator it docent take off like it should and it build up rpm before it jumps into second gear but after that it shifts pretty good and when I gas it to to about 70 mph the abs and brake light comes on...