I have a 2006 GL 1800 and I am getting poor radio reception. I removed the seat and I found a grey cable coming from the cb transceiver mounted in the trunk connected to the cb antenna on the left side. The cable coming from the am/fm radio antenna on the right side was not connected to anything it was just stowed. My question is isnt there a cable with a socket coming from the audio unit that connects to this antenna on the right side in order to get am/fm radio reception and where is it located as I could not find it.

The antenna wire for the radio goes all the way to the front under the top shelter to the left side of the radio. I don't know what you have at the rear but it's not the radio antenna unless someone replaced the antenna and didn't fish the antenna wire where it goes. Are you sure it is coming from the radio antenna. Do you have a picture you can post?
This is the CB connection to the CB antenna
http://im1.shutterfly.com/media/47b7df03b3127ccec078061793b300000010O01CcNWzly0Yg9 vPhw/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/