That sounds like a rod bushing going. I would not run it until you replace the rod. You may have ran it too lean and over revved it.

Last weekend I was trying too dial in a new FM 21. I had great low end but no top. And temps were getting up there. I turned the HSN out 1 full turn and the LSN in 1 full turn. My top now SCREAMS and I still have good bottom. My temps also dropped 40 degrees! I will check exact settings but I am somewhere around 1 1/2 turns out on top and a full turn or so in from flush on the bottom. Stock settings seemed off.