Originally Posted By: kelpie
I'll have to disagree with the backpressure posts. If you lose the backpressure, you'll have to rejet or you'll have less power than stock.
Not really on fuel injected vehicles. On carbed vehicles reducing backpressure did tend to lean out things, but the backpressure reduction was always good for a net HP gain.
In highschool (rural South Texas to set the scene/mood) we would get cherry bombs or whatever glasspack was available installed on our trucks (cars were unheard of among males). Right after install the truck would be brought home and the sound critiqued by friends and family. If it wasn't loud enough, the truck would be driven hard to heat up the mufflers well, then a garden hose, on full blast, was run up the tailpipe to flood the glasspack and fracture the glass filling allowing it to either compact, or blow out the rear. Truck was started again, water blown out and the sequence repeated until the sound was "just right".