Brand new to the forum. Bought the truck and the noise I am trying to figure out was not present at that time...I knew it had a manifold leak when I purchased it, so I took it to the muffler shop and had the guy install a new manifold and gasket. He also cut the old clogged CAT off and installed a new flow sound muffler and all new pipe from the Y pipe back. New donut gaskets on both sides. When I picked up the truck I noticed this chirping coming from the tail pipe so I had him put a different muffler on..still chirps and the guy says he can’t hear it. I have attached a YouTube link that shows the same noise I am having but mine only does it under a slight load..idle sounds great and so does high rpms. Any help would be greatly appreciated.

 

Sounds like metal to metal contact to me. It could be many things. Might be something simple like your starter heat shield rubbing on the exhaust manifold (very doubtful) to your Cat heat shield making noise. Are all the exhaust system insulation rubber parts hangers looking okay? I can sure as heck can hear that noise so your muffler guy must be deaf.

 

I have checked for all of that and all of it seems to check out.

 

that video is not of his truck but someone else.