Yes, glass packs are very restrictive. I believe that sound you are talking about is the "redneck" truck sound or "ranch truck" sound. Very loud and annoying. A good dynomax or flowmaster muffler (even just 1) on a larger diameter pipe will make more power than duals with glass packs.. The best sounding car iv'e ever heard was a 94 firebird formula with a 383 stroker Lt-1 and a 3 inch mufflex system with a flowmaster 2 or 3 chamber ...pure sweetness to the ears