Could also be your amp. I had the same problem with my Fosgate amp. Grounded it to sooo many places. Then i took it out, put in an Alpine amp, and the noise was gone.
Also, about 4 years ago, i installed a Jensen (don't laugh) amp in my work truck. Noise like hell. Returned it, bought a Pioneer amp, and the noise went away.
Moral of my stories? Amps caused all my noise troubles. Good luck!
