I am new to this forum and new to the vortec family. i have had the 350ci for years and finally upgraded to the new body style (2007.5) i noticed this noise from my truck at first and i have yet to figure it out and i need help! it has 143,000 miles, rebuilt transmission, rebuilt transfer case, and fluid change on front and rear end. after i get to about 5 to 10 mph i notice a noise and it only happens when im giving it gas or when im going down hill. i think it is coming from the engine because when i let off of the gas and the engine is slowing the truck down, and when the engine starts to accelerate is when the noise returns, in the happy medium it is quiet as can be. the noise is like a cold air intake on a 4 banger at WOT.

thank you in advance!