Can't figure out what the sound is?

Okay for some unknown reason i have a sound coming from my motor and i can't understand what the hell it is. The sound is like an exhaust leak but it only does it when the car warms up and i have been driving it for a bit. I know it is not a rod or lifter. It doesn't make the sound when it is in park and i rev on it. Like for example: i slow down (automatic AoDE) going around a corner and i just push the gas in to speed up, not hammering it, and it seems like it bogs down and starts making this noise. My dad thought it had some water in the gas tank or he thought i got ahold of some crappy gas, so i changed the gas filter, filled up somewhere else, and put some stuff in the tank to make sure if there is water in there, to clean it out. Then my other friend i know says that i either have a clogged cat converter or i need to regap my spark plugs. There is nothing done to the car besides k & n air filter and flow 40 series mufflers. If anyone has had this problem or can point me in the way of what i might need to check let me know please. Thanks!


David

sounds like an exhaust leak but goes away when i ease into the gas. by that i mean barely pushing it in. But it doesn't do it when i have the transmission in park and i rev on it.

I will check it in the morning and see what i find. Thanks for the help!

David