Subs Play Exhaust Noise

Alright, I really don't know all that much about car audio stuff so I was hoping you guys could give me some advice. I have 2 MTX subs and an MTX amp in my car that I got from a friend (not really sure of their condition), and if I try to tune up my subs at all with the amp, they give off this annoying "humm" that is from my exhaust. Anyone know how to get rid of this?

I have the wires going from the battery, over the passender fender, through the firewall, down the center console area and under the passenger seat, then back along the wall to the amp that is located in the driver's side "pocket" across from the spare. I don't know if it has something to do with my set-up or the components or what.

Make sure you have a good ground first of all. And it should be as short as possible.
Sounds like you are getting interference from your engine/ignition(not your exhaust).

Sounds like dirty sound. They make noise filters you can get if thats the case. Radio shack has em

Anything in particular that I should ask for or know about my set up (i.e. wire size or amps or anything, certain kind of filter...) before I go asking for a filter???

Not really, the filter will run inline with the RCAs. I think the problem can be fixed elsewhere though make sure you have a solid clean ground and that your power cable doesnt run next to the RCAs

This happens when your signal lines (the ones that run from the head unit to the amp, usually RCA) pick up electrical pulses from the car's electrical system. The pulses come from the alternator, and are distributed pretty much anywhere there's a +12V wire. If you run your signal wires near your power wires, they can pick up this pulse. It gets carried into the amp on the RCA lines, amplified, and then you hear it from your speakers.

A filter is the cheap way to fix it. It will remove the pulse from the signal line so that it doesn't get amplified. In some cases, it will only reduce the volume of the pulse; you can just put another filter in the line to eliminate it completely.

Unfortunately, a slight loss in sound quality occurs when you run the signal through the filter. Most listeners won't care. If you happen to care, a better solution would be to make sure that you're using shielded signal lines, and make sure that they are not run parallel to any power lines. If you can't avoid running the wires near each other, you can add additional shielding yourself by wrapping the signal lines in aluminum foil (or any other conductive metal).

The typical wiring setup has the power for the amp running down one side of the car, and the signal to the amp running down the other side.