Carb problems following needle shim mod

[mrlmd1]

Welcome to the forum. Get used to it.

Do not use 91 octane, the bike is designed for regular gas, 87 octane. That may be part of your problem. Empty out the gas and put it into your car and put in fresh regular gas.
If after you switch to regular gas it still runs rough, why don't you then replace the new spring for the carb? it may be a touch out of spec or hanging up on something in there.
If the bike was running fine before you did the mod, and runs like crap after you did and then undid it, it has to be something you did, right? Retrace your steps, look again for air leaks. The fresh gas and new spring may fix it.