weird soud from my engine

[silverv6]

I need help guys well for the past month or so theirs this sound coming out of my engine. yesterday I opened the hood up and I turned my on. Well I reved my car up and a weird sound was coming from the headers. Well the sound only comes out on the passanger side but not on the drivers side. it sounds like exaust like it it was coming out from the headers. then i looked down under the car on the passanger side and it can hear it also. Wat can it be??? Well one time this guy told me it sounded like an exaust leak. Well if it is wat could of coused this??? cus its just on the passanger side.