Ok, everytime i am at a stop, with my foot on the brake, there is a fairly loud rattle coming from the engine bay (arround the master cylinder). If i release the brake, it stops... then when i go, it rattles faster and fades away at arround 2k rpm... it has been doing this for some time now, and i am clueless as to what it could be. Im not really worried about it, its just really annoying. Any ideas?

 

auto or manual?
if manual, could be release bearing rattling. This isn't too big of a deal as long as you get the clutch to fully disengange, you'll be ok. This is probably not the case with yours as you state it's relevant to your brake position.

Otherwise, maybe just an idling issue, or your alternator might be hesitating to put out power. Maybe your battery is going, seeing your list of audio mods. Try shutting off all unneccessary loads, have your amps/subs off and try tell us if you still get this prob.

Maybe your intake is rattling on something

Otherwisem I need to hear it, but hope this helps anyways.