I have a 2003 carbed 150. it has had no problems. ran it yesterday----8 miles WOT---ran 5800 rpms---60 mph upstream---ran as good or better than it ever has! when i down throttled i heard a knocking when i ran it about 4000 rpms. idled great. when i ran back downstream ran great again at WOT---but if I ran it at about 4000 rpms I would hear a knocking---at 4800 and above seemed great

any ideas what is going on. I use ethanol additive and even run xd100