So I finally got to upgrading my stereo in my 09 DC with JBL system. Itsmy first stereo build/install. I built an amp rack and mounted the JBL amp and my 400w amp to it, then mounted my 10" sub in a truck box to that and put it behind the back 60 part of the seat. it fits perfectly and is solid. covered it all with black carpeting and trimmed the black plastic to fit around it. almost looks OEM. I then installed my Pioneer avh P4300 using the Metra JBL harness that allows me to use the jbl amp to power the speakers. it all works fine EXCEPT the volume fades in and out randomly. its not to the point of on and off, but more like a loose connection or bad wiring. I cant duplicate the problem though. it happens on its own. volume level doesnt matter, source doesnt matter. the only thing i can think of is either the Metra harness is bad or just not good to begin with, or the JBL amp isnt stable enough to power the new headunit. I double checked all my connections today. I cant figure it out. any help is greatly appreciated. hopefully i explained the problem well enough to get an idea.