I'm posting this on behalf of my boss man. He has a 2007 Ram 5.9 cummins. The other day i removed the cat/resonator and welded in a straight pipe. He says ever since then every single time when switching from Drive to neutral, Drive to park, etc. the rpms shoot up into the 2,000s and then jump back down to normal. When in drive it feels like the truck wants to lunge forward with out touching the accelerator. He has to stand on the brake so it wont move... Also he said he started going up a steep hill and he said there was no acceleration. He had it to the floor and it was just idling. He said once he was back off the hill the accelerator started to work again. Anyone have an idea of what may be going on?

Thanks