I have a silverado crew z71 4x4 and when I stop and go from stop sign / red light and I don't gun it I am getting a rattling or knocking noise from the engine.

I have this set up- VORTEC 5.3L V8 SFI GAS ENGINE W/ ACTIVE FUEL MGT TECHNOLOGY

Any thougths? Any fixes like an engine treatment.

I use 99.9% Exxon regular gas so it's not like i'm going cheap on the gas.

thanks