Engine noise problem

I have a cadillac seville and I am getting a whining engine noise that gets louder as i press the gas. It started when i installed a new TV Tuner. The thing is though, even when i unhook the RCA's from the tuner, i still get the sound. As soon i unhook them from the head unit, the sound is gone. So i know the problem in generating in the RCA cables. I replaced them with new ones, and installed a ground loop isolater, but the sound istill there. Even when i completely unhook the new tuner, and just leave the cables hooked to the head unit only, it still is there. Any suggestions? Any help would be appreciated.

Just thought of something, are you using a RF Modulator for the tuner? If you are thats more than likely your problem. I have seen way too many of those be bad straight out of the box.

No, my power wires aren't even running down the side of the car b/c the battery is under the back seat. I will try to reground the head unit, only the problem doesn't happen if i hook my dvd player direcly into the head unit, nor does it happen on the radio, or on the CD Changer which is also hooked through the head unit. I have already tried regrounding the tuner. I have been told that it may be b/c i have TV antenna hooked up in the rear window. At one time, i ran the rca cables outside of the car, and back into the trunk, and just left them hanging there, and i still heard the noise.

That only means the problem is being created by the impedence of the long cables.  If the noise changes with the cables location, then it is probably induction from some RF source in the vehicle (since you say you tried differnt cables, so you've ruled out the most likely cause which is damaged cables.)  If it does not matter where the cables are located (which is what I thought you were saying) then it has to be a bad AUX input on your HU.  The noise is being caused by the total length of the cable attached, which is being demonstrated when it stops with shorter cables attached.  I suggest your HU is faulty.   What is it, BTW?

The outer ring or shield conductor of the RCA cables.  It sounds to me like your HU has a bad ground plane on the pre-amp output creating a ground loop in the pre-amp signal.  When you plug in the DVD player it grounds the RCA's well enough to overcome this, but the tuner does not. 

Try an experiment: disconnect the RCAs.  Play the system so you hear the noise.  Connect a wire from the outer ring of the RCA plugs to ground.  You can use the ground terminal on one of your amps.  See if the noise stops.  If so, then my guess is right.  If not, then there is something else going beyond my ability to troubleshoot over the internet!