I have the same infamous midrange bog too with my shee. It isn't a passion motor either. It runs good up top and the plugs look great with 460 (yes 460) mains on stock carbs. I'm not even going to attempt to get it running the way it should be until I get some 34mm intake manifolds and a set of cut t3's. I got 34mm roundslide mikunis too so I guess I'll be the second person with these carbs trying to get them jetted right. I guess I'll be posting in this thread more when the time comes. I know how yall feel though. I spent alot of time changing out needles, syncing the carbs, and changing out mains without getting rid of the bog.