You will have to actually bend the underside frame, not a heat shield. When you pull the stock cats (at least on a G35), you'll see where you have to modify the frame. It's not a whole lot, and it's nothing structural, so there is no real issue.

Check the flanges on the Y-pipe before you go grinding away. They may have changed flanges since I bought mine back in August 04.

 

GREAT NEWS deviant1... Can't wait to install mine!

there were also birds chirping in the other Helix vid... i think they like the sound of the Zzzzzzzzzzzzz