tweeters crackling during braking

I sure hope someone has an idea here. This is driving me mad. A search didn't help. Boss CX350 4 channel amp wired to 4 JL 570CXi speakers. I added a set of Polk db1001 tweeters to the front, connected right at the amp terminals with the front JL's. When I apply the brakes, or when hitting bumps, both tweeters crackle. The front JL's do not. Wiring issue? Speaker issue? They sound fine when they're not crackling, though they do emit a hiss even with the volume all they way down. And no, the gain is not cranked. Would snipping the attenuation loop on the tweeter crossovers do anything? I could try re-routing the wires I suppose, but there really isn't much wiggle room there. They're mounted in the bottom of the a-pillar covers. The right side wires comes down and run under the dash along the carpet line. The left wires just come straight down to the amp (mounted behind the pedals on the drivers' side firewall).

Forgot to say it's a 2011 Ford F250 XLT Crew Cab.

You most likely have a ground problem, either in the amp, the head unit or on the head unit preamp output.  Check the Hot topics forum and first make sure you have good amplifier and head unit grounds.  And do not remove or modify the tweeter crossover in any way unless you want to burn them out and buy new tweeters soon.Support the12volt.com

I'm using the factory head unit. I used a PAC OEMFRD24 to give me my pre-amps which go straight to a Clarion EQS746. That gives me pre-outs for the front, rear and sub outputs. The grounds on the EQ and 4 channel are fine. Like I said I have no noise from the front channels, just the tweets. I ended up running the tweets off of the unused front channel wires coming from the factory head unit and bingo, no more crackling or hissing. Still sounds fine so I'm just gonna leave it like that. I'm not sure what the deal was but I'm glad it's cleaned up. I guess those tweets just didn't agree with the cheapo amp.

Amp is behind the pedals on the driver side firewall????????  You might want to rethink that!