exhaust drone/harmonic resonance

Anytime you dump the exhaust under the car, you are releasing all the sound under the car which echos off the road and back to the bottom of the car.

Ever driven across an expanded (mesh) metal bridge?? Ya notice how alot of the noise of the car disappears??

Run full pipes out the back and some relativeley quiet mufflers and you will be much happier. Sounding like a Pro Stock car gets old really quick and dumps (to me) sound crappy on the street....
Ever realize why ricers sound like crap?? The exhaust system ends at the muffler. Listen to an old MG-B. The muffler is under the seat and there is about 3 foot of exhaust pipe after it.