Welcome. I have a 1993 and the only issues with the carb that I have had was a thumping at wide open throttle. That was caused by a lean condition/ not enough gas for that speed. My carburetor boot was bad so I was getting too much air which only really affected it at WOT full speed. I sealed up the intake and never had another issue. The next size jet bigger may not hurt but since these bikes are not ran WOT much it would probably just hurt your mileage without much increase. Your lower rpm issues I think you probably didn't need the shim. Using the choke isn't bad. If mine has been sitting even when it is hot I usually have to put the choke about 2/3 out, it cranks and push the choke off and take off. I tried another carb for experimental purposes and mainly it was too rich. I reinstalled my stock carb and it runs great. Play around with the air fuel screw as it does slightly affect some of the other speed ranges also. At least these carbs are easy to get to. Good luck.