odd engine noise problem

a customer came to me with an 03 accord, he had a 4 channel amp hooked up to his stock h/u and had crazy engine noise even had a humm with the key in the on position however not in acc. he wanted a deck and to have me look over the amp install to see if it was done right. it looked ok however still had engine noise allthough less with the aftermarket i put in. my first thought was bad rcas or ones ran close to a power source. so i temp ran them from the deck straight to the amp by just laying it over the seats and whatnot, however if anything the whine was worse, i then checked the ground which looked good but i moved it just for fun. any input?

where was the amp remote wired into.

alotta times you'll get  residual power interferrence. or is it hooked into the factory harness

sounds like one of your grounds is geting interfearens probebly your deck ground. what  kind of noise is it what dose it sound like. dose it sound like interfierence or dose it sound like a failed pieace of equipment.