Hey i have a 1990legend with a stock deck. I pulled out the 2 rear speakers, and put a 10" Kicker sub in the trunk, I powered it by the rear speaker wires. SOUNDS FINE. But when i turn it up alittle and stand at the back of the car, i notice a sound from something under the chassis rattle. (near the muffler) i tired to hold the muffler but i still hear the rattle, so i know its not the muffler.