Noise from recent install

Hey guys. I just finished an install for a buddy of mine in his 02 Civic and something happened that I've never encountered before. The following components were what was installed:

After completing the install, everything was working just fine. Then after 3 days of driving around with the new system and everything working fine, out of nowhere this really bad engine noise started up that I can't get to go away. It's a combination of whine plus very soft "popping".

I did the install the way I always do, power wires+remote-turn-on along passenger side and rca's + speaker wires down the middle. The deck was installed using a harness. I made a single ground connection(4 ga wire) to the car and fed the amps + cap through a distro. block .  The only troubleshooting I've done is relocate the ground location(if you're familiar with a 4 door civic,  I placed it right behind the back seat as well where the rear seat belts are attached to the car) and there was no change what's so ever. If I unplug all the rca's the noise goes away(not sure what this tells me). What other things can I try?? I'm going to borrow another amp to rule out "bad amps" as the possible cause. Any suggestions would be greatly appreciated. TIA 

I would have posted this in the "Ground Q/A forum" but seems like nobody posts there anymore.....

this is often the results of ground foils burning open in the audio stage of one of the components... this may require swapping of items to try to narrow down which is the culprit component, which is usually the HU.... try another HU if possible... or try grounding the shield of the RCA to see if this changes the problem at all... if it does, take it to a qualified tech to be looked at.....

it's often tough to try to troubleshoot ground issues online... you just have to try this, try that, etc....