Exhaust!!! HELP

[ODs_SE-R]

I just picked up my car from my buddies house who was putting my headers and exhaust on. I bought generic ebay headers and full magnaflow exhaust, Everything is put on and ready to go, i was driving it home last night and im hearing alot of noise from the headers, i am 100 percent positive i have an exhaust leak somewhere. When ever i give it gas im hearing alot of noise from the headers..is that normal??? sounds and drives great, but was just wondering what that noise might possibly be. If anyone could help me please, i wan to get this fixxed soon. My buddy and I are going to take a second look over what he did to see if the gaskets are good and find out where this noise is coming from. Thanks for any help guys!!