I've been having issues with engine noise ever since I upgraded my front stage. Changed items include:

Alpine SPR-17s
Alpine PDX-4.150
Kicker KX3

I've isolated the issue to the crossover; with the RCAs going directly into the amp there's no noise. RCA to crossover to amp produces noise. I use a distribution block to ground both of my amps to the chassis. I've tried moving the crossover ground, but to no avail. It's been connected to the distribution block, its own spot on the chassis, and directly to the battery for diagnostic purposes. I've read, re-read, and followed The Ten Commandments of Noise Prevention and seem to be stuck. I guess I'm here to see if there's anything else it could be, I'm open to all suggestions.