You can run a new remote wire from the back of your deck straight to the amp(without having to hide it) to see it the problem still persist. Make sure the connection is tight at both ends.

I haven't read your other post, but how did you hook up your amp? What kind of wires? Did you give it good ground? Are the wires big enough? If you have a friend who already has an amp in his car, maybe swap amps to see if it is bad or not. Keep us posted