So i got my headers installed so
 

Will i still see a big difference if i were to change my stock rusted and mishapped and formed exhaust from the y pip and back?Cuz i got hedman headers.I was thinking about going with the hooker cat back or something thats really thoraty.

your best best to get a new catback like said, high flow cat or cat delete pipe and a new y-pipe thats mandrel bent.

The headers arent going to add much if anything if you're still running your lo3's 2 1/4" cat back pipe, or if you've still got the original cat. Im assuming your headmans are 2 3/4" or 3" so my suggestion is like form350 said, get at least a hiflow cat, and then finish it off with a nice cat back.

If you fix one thing on the exhaust, in order for it to work you must fix all things.
-chuck