I didn't read anything about it stopping at a higher RPM. If I would have known that..... What I read could definitely be octane related. My stock 400 will ping when you get on it if I use 93 octane. It goes away when I add some 110. Maybe Doug is trying to get away with 93 in an engine set-up that will not run with that low of octane. Easy things first is my tactic. It wouldn't hurt to hear an octane to compression reference to get things in context.