Agleon

I used to own a 07 GT with Pypers H-pipe and Stingers about 2 years ago, I have just now picked up another 07 GT with no mods and still have the same rattle going on. At times it may sound like it's coming from the center dash, Other times around the shifter area or top of the dash.

This isn't a squeak or weak rattle that I could just live with, It is a metal sound.

Nuke

1. Check the TSB for the tranny separator plate issue
2. Re-torque the pipe clamps (midpipe and axleback) an extra 1/2 turn or so
3. Look for exhaust hanger-to-frame contact and adjust pipes, if necessary
4. Check the heat shields

illini4

Might be the exhaust pipe hangers attached to the transmission support. If they are there, cut them off. They are only there to hold the pipes in place during factory assembly. After that they serve no purpose. The rattle may be the overdrive button in the shifter it it's an automatic. There's a TSB on this.