1st there are two types of glass-packs. Chambered and non-chambered. This is were flow and sound comes in. If you want to get a really low tone . Get a NON-chambered glass-pack and put in place of your cat converter. Then put on another muffler , Turbo's work the best. That WILL make a really low rumble. Beleive it or not a non-chambered glass-pack is very close to what a resonator. It is a 2 chambered hush box designed to take the raspy noise out of the exhaust AND prevent kickbacks or pops. I had this set on my 98 SVT Contour. It had a 2.5 V6 and sounded very aggressive for a little 2.5