Will removeing the elbow connecting the air box to the wheelwell and switching to a K&N filter safely add horsepower?

Has anybody run into any voltage issues running an aftermarket stereo system?

I would like to try and trackdown the previous owner. There are two wires next to the front seats that dissapear into the dash. One is a small on/off toggle switch that successfully makes the radio go all fuzzy and the other is a black piece of monster cable that terminates w/ a headphone type jack. The VX originally came from Hoffman Isuzu in East Hartford, CT and then lived in MA somewhere.

Any info would be helpfull. Thanks!