The acc wire feed is the yellow that is found in pin I.The way to test for the feedback loop is to shut off the radio with it's power button.If you get a drone or "motorboat" sound that is the feedback problem.The toggle switch option will work for you to stop it,however it usually creates some turn-on/turn-off thumps.Still better than the other option.Good luck.
My yellow wire is actually in pin 2 position, but based on some diagrams and stuff I just searched for, looks like that is the correct wire.(yellow in pn 2)