RE: .91ax?
You will be fine. The guys that got good ones can't be happier. The guys that got bad ones won't use them again. I sold mine today in the plane it was in. I was going to just sell the engine but sold my 2 33% birds and he decided he wanted that one too. That works. I hope he has good luck with it. Heck, it could be the fuel, I have seen that before too.
Oh well, I will get the 120 AX if they don't ever do a 91. Would rather have the 91 though. I wonder how an FX would run with an AX carb? HMMMMMM< theres an idea I need to do some research on.
That may be a really good combo.