Just got it back from Chad and mine was shimmed wrong also but that was fixed. I use a P4 plug w/30% Byrons. When I try leaning the LSN to where it needs to be it constantly chatters, never going to a smooth idle. Really, with my other high end Italian mill I don't have to seal anything, does the ExTech need to be sealed everywhere? The carb seems well sealed with 2 O-rings. I dunno, maybe if all else fails.