first thing, pop your hood and flick your heat sheild on your exhaust manifold. If it buzzes, that's probably it. Tighten the bolts. If not, jack up the car and start hitting the exhaust every so often with a screw driver until you hear it buzz or rattle. Then either unbolt it, tighten it, or rip the sucker out. It doesn't add any noticeable amount of heat to the cabin... Anyone that tells you it does, will also tell you that a cat back system is enough to make your floor boards melt.