Hello, I am new to this site, and also a new Cummins owner. I recently bought a 2001 Ram 2500 Diesel. I just had 4" exhaust installed, and when I left the shop, it seems to be running rough. When I drive light the truck runs fine, but as soon as I hit the accelerator hard it starts to buck and sputter, it feels like no fuel, or transmission slipping, once I let off it smoothes out and runs fine again. I noticed it doing this sort of thing on the highway with the A/C on a couple of weeks ago, but hasn't had any problems since until the exhaust was done. Is this the fuel pump? Or the lift pump? Or the transmission? I just read on how to check the codes, and I'll do that tonight, but if anyone has any ideas on what this could be I would appreciate the input. Thank you.