slight ticking noise when running,

My new system has developed a very slight ticking noise. It's not a whine, it sounds like a taser, but much quiter. It's mostly from the rear speakers, but is present in the fronts to a lesser extent. And of course, I can only hear it while the motor is running. It's quiet enough it doesn't affect the sound, I can just hear it if I turn my head right. I'm pretty sure it is ground loop noise... However, I don't believe this noise wasn't there before the amp went in. Should I add a ground loop isolator or try simply grounding the HU case to body? System... Aiwa CDC-X217 Pioneer 6.5's off HU Alpine MRP-M500 MTX subs 8 gauge power to amp along driver side with 8 gauge ground to clean body bolt 2 x 8 gauge battery ground cables 6 gauge body to engine Shielded home theater RCA's running along passenger side

Possible bad spark plug wire.

Good idea. I'll check them tomorrow. Anyone else have an idea?

Easiest way to check is to open the hood in the black of night and look for sparks.

The old wires that were on it when I bought the car went bad down in the tubes where you can't see anything. I'll inspect them real close in the morning.