I have the Sudco / Mikki catalog and was looking into needles and slides and they are pricey. The slides were about $30 and needles were around $20. I get my jets local for $5. Just saying, it's not like dialing in the carb is cheap so be sure that there's nothing else wrong with it.
Do you have any way to hang it on another bike to see how it works? I still can't see why it doesn't work better if you're in the ball park, 140 MJ and a 20 LS should be pretty close.