I checked almost all possibilities where the rough sound is coming from. The entire exhaust has no leak but the truck sounded like theres a hole in the exhaust especially when I start it in the morning. It was mentioned before somewhere here that the sound is like a tank (i forgot the name of the tank, lol) It quiet down when engine gets hot but broken muffler noise still audible. Can Catalytic converters make that sound too? Thanks

 

Cats usually fall apart on the inside and rattle. Sometimes a leak sounds like a steam engine train. That would be air escaping from a crack or leak. Sometimes the bolts vibrate loose coming off the engine manifold. There are 3 bolts on each side. From there the Y pipe connects at the rear crossmember where the single pipe connects to the muffler. If it's leaking, it has to be at one of those places, otherwise you may have a crack, or have to look higher up where the manifold goes up to the engine on each side. There are bolts there holding each manifold on.

 

My buddy and I both have the noise that the OP mentioned. Any updates/thoughts here? Thank you.

 

I've seen those manifold to y-pipe gaskets just blow out the side. That would be my first thing I'd try.