I also have one 90 that i have used a few years with no problems. I do have all the tanks under pressure and out of the 4 90s i have two have the double screws on them. I emailed Ken Enya in japan and even though my 90 says in the manual to use the # 3 plug he said the # 5 plug was required for this engine and he sent me three # 5 plugs. I have set the carb as rich as i can and it still leans out and i come down dead stick any time i try to fly. I have several engines ranging from radials to twins, saitos, os and never saw this before. The gage in my enya 90 tool kit is .005 and the kit for my os twin is .005 min to .010 max if the gap was that far out it would run rough at idle but it is perfect.

I took the barrel out of the carb cleaned out everything and didn't see any venturi. I will try a 14x8 APC prop and see what i get but my hopes are not all that high as i have tried 13, 14 and 15 inch props.

Thanks
Dave