Is your check engine light on? Mine was doing the same thing and had the CEL on, the code was for a leak in the evap system. I changed the solenoid beside the drivers side of the intake and the canister on the side of the fuel tank, both easy jobs as long as you are careful with the clips. Cleared the code and it is like a new truck. A vacuum leak like that will lean out the AFR and the truck will feel like a turd, especially at low rpm.