Ok Blazer folks. I need your help. Put an aftermarket stereo in and now the FM oscillates from crystal clear to a muffled muted sound. This happens with local and distant stations. The stock unit did not do this. Here is what i have tried so far. A new antenna & antenna wire. An extra ground wire from the stereo chassis to the truck body. I tried an FM signal booster. Removed and replaced the stereo with two others ranging from quality stereos to budget all had the same issue.