speaker mystery

I drive a 92 pontiac bonneville with with infinity kappa components up front and kapa 6x9's in the back,they were powered by a garbage legacy amp, two l7's in the back powered by a kx1200.1, and the head unit was a deh 4600.  With this setup I had a ground loop problem and i added a ground loop isolator and upgraded car to ground and ground to alt and it left me with pretty much no noise.  This is were the funny part comes in I upgraded the head unit to a DEH-P9800BT and interior amp to eclipse xa4000.  I initially hooked up everything without hiding all of the wires and the sound was clear so i dropped the ground loop isolaters and the sound was perfect.  Leading me to believe the noise I was getting before was due to cheap components.  Then I tucked all of the wires away (away from the power) and when I started my car it went back to having a terrible noise through the system.  I cant' figure out for the life of me what caused it I didn't touch any grounds or anything.  I have tried taking the wires back out and going back to how it was before I tucked the wires and nothing I do is getting me back to that perfect sund I had before.  Please anybody and everybody help cause this is really stressing me out?

You need to ground the shield of your RCA cable   use this picture for a guide    the end of the yellow wire needs to be grounded

http://www.bcot1.com/images/rca/asdf.html

If grounding the rca's will fix the problem that still doesn't explain why it worked perfectly without it before.