I have seen many threads about sidepipes being too restrictive but I'd have to say the undercar exhausts are even more restrictive, especially given the extra length.
My car (#1660) has 2.25" pipes from the headers to the tailpipe and I'm not an engineer or motorhead but that seems just too restrictive. The factory knows what kind of engines are being installed in these cars but that is what they supply.
I've never had any clearance issues but I did raise the ride height a bit for the initial NJ safety inspection and have not yet lowered it back down.
This is my answer to a restrictive exhaust:
