Moped Army

So I had a thread on here a while back about my 99 Tomos Targa LX having a sputtering issue around 40mph. The general consensus was fuel starvation. Well I just swapped in Jcams 20mm Mikuni with the proper jetting, plus clear fuel lines with a filter, and I still get the same issue. I can see that there is plenty of fuel in the line/filter, so it can't be that.

Plus it hesitates for a second when starting from a stop, or when I let go of the throttle, and re-apply it. It gets up to speed fine, but then sputters a hell of a lot.

I've checked for air leaks, done plug chops, etc etc. Any ideas? Timing hasn't been changed since I did the Alukit upgrade, and it was running peachy till then. Thanks for any help.