Hard to know exactly what would happen if you removed the resonator, depends on diameter, length, where in the exhaust system it is, and what type of resonator it is. Resonator's dampen certain frequencies depending on a lot of factors. It "could" just make it a bit louder, it "could" also change the tone/sound. Typically manufacturers use resonator's to help deaden any frequencies or unwanted tones that still exist with a muffler. Usually resonator's help to take away the raspy higher frequencies that give 4 cylinders that "ricy" sound. But, with a muffler I doubt you would notice much tone change. Usually quality exhausts have the resonator on there for a reason, you definitely don't want to open the door for extreme drone all the time, that = massive headache.