I had the same problem. Would only squeal when mine was hooked up as a single. NOT FEEDBACK. Dealer tried to tell me that because he didn't want to find the problem. I finally took off the seats and there is a plug that was ever so slightly pulled apart. Pushed it back together and put some electrical tape on it and no squeal. Went 1800 miles to Sturgis and back and no squeal. Ran the IC at the same level I always had.