Evan --
I just happened to see a post on the Tomos forum that said the A55 carb has a mixture adjustment screw. So I tried tweaking it, and solved my run good / run rough problem. I took the bike out on a long stretch of flat road, ran it until it started running rough, backed the screw out 1/4 turn (roughness was worse, as I expected), then started turning the screw back in by 1/4 turn increments until it consistently ran smooth. You might try that and see if you can optimize your carb adjustment.