loud high pitch noise and loud static

I have tried a lot of things and search an number of places before trying this. I have a 2003 Nissan Altima. There are two apms a 4 channel and 2 channel both older Rockford Fosgate amps. The head unit is a Poineer DEH-8600. This was working just great but I wanted to upgrade the head unit to something that would operate a Ipod correctly so I got a Pioneer Elite DEH-P980BT. The Amps have 8 gauge ground and connected to body and all paint is removed from both ground points. The Power is 4 gauge from the battery to a distribution block and have a 1 farad cap hooked the block also. Since all the connections are the same I just unplugged the old HU and plugged in the new one. Turn the car on to test and I get a loud high pitch noise no matter the volume on the HU. Turn it off and I get a loud static noise as the amps turn off. My initial thought was a bad HU so I unplug the new one and hook up the old one, same thing. Now I am confused. I get a new harness and redo all the connections and relocate the ground, same problem. I tested by undoing all speakers and testing each channel one at a time to make sure its not an issue with a speaker, but no change. Thought it might be the Amp so I hooked my Ipod direct to the front input to the 4 channel and sounds just fine, even it I change the amp to 2 channel input still sounds goo through all 4 speakers. I do have a slight alt whine this way but only can hear it at very low volume or no volume. Then I thought it might be the RCAs so I ran a new RCA from the HU to the amp externally so not by any other wires same issue. I disconnected the 2 channel amp and try again, noise is tad lower but still there, but I did notice that if Car is running or key is on position its much worse then if key is in Acc position. I have checked all connections on the amps and coming into the amps and are still tight. I am stumped, I would think its the HU but its does it with both. Any help or ideas would be greatly appreciated.

ive been told not to run my power lines with the rcas did you? this sometimes will cause issues. you have an 8 gauge ground, but a 4 gauge power? ive been told to match these. bigger is better. in this section they have a how to upgrade the big three might want to look at that. pioneers are also know to need really good grounds at the head units. i had this happen last year and took it to a pro turned out my ground was not good on my head unit. i beefed that up and it took it away alot but noy 100% i then added monster xln connects i died no more issues. im a noob so im prob in left feild,these guys really know their stuff im sure a person with more exp will respond good luck.OWWWWWWWWWWW you said you discharged the cap!

Just to clarify, the 4 gauge it from battery to block and 8 gauge power from bock to amp.

i am an idiot wrote: Pioneer decks are famous for this problem. There is a blown surface mount fuse on the bottom of the circuit board of your radio. The fuse connects the shield of the RCA jacks to ground. When the fuse blows your patch cords have no ground reference and this causes noise. I am not famifiar with that actual deck, so I can't tell you where the fuse is or how to get to it. The following will fix your problem. Solder a wire onto the shield of one of your patch cords. Ground the other end of it to wherever you got ground for the head unit. If the link appears to be dead you will have to correct the end of it. Notice what is says here and then notice the last few characters. The underlinig feature of this site changes the end of it. http://bcot1.com/images/rca/IMG_9227b.html They put this fuse in these radios to protect the radio in the case of a shorted transformer in an amplifier. A shorted transformer that could cause damage to a deck happens maybe 1 out of every 200 amp failures. If somebody ever meets the engineer that put the fuse in the decks, could you please tell him thank you for me. No serioiusly I really want to thank him.

Thats was exactly it. I am sending back the new HU so I can have this fixed. If I continue to have an issue I will try the other idea. Just curious can you do the same thing at the amp end? It seems like it would be much easier to do it on the amp end instead.

You can do it at the amp end but it will cause a ground loop.  You can try it at the amp.  I have seen it work there, but most of the time it will get rid of 90% of the noise.  When done at the radio, it gets rid of all of the noise.