Update.... New (used) coil that tested good is in... no difference in running. So the old coil had an open, but it must have been on the secondary and it must have been small enough that it jumps with no problem. Who knows how long it would last though... anyway, a good coil is in now.
I continued playing with the jetting, and was all the way down to a 152 main, and the choppy got less and less each time I dropped a size. Instead of going down to a 150, I found a new FMF Turbine core silencer on ebay, and bought that (I already had the gnarly expansion chamber). It went on tonight, and that seems to have cleared up almost all the rest of the chop. I didn't warm it all the way up to keep from bugging the neighbors.
Amazing the difference it makes, the thing does pure throttle wheelies in third gear now... it feels like my neighbors 450. Fun stuff for sure.
The other thing I did was fix my float height. They were *WAY* off. That explains why the bike drooled gas all over the place every time it was leaned over even a moderate amount. No idea if that changed the runnability as well, or if all the improvement was the FMF silencer.
I also adjusted the float level in my sons KX-60. But now it bogs at WOT (it didn't used to). It doesn't drool gas like it used to, but the bog has to go. I'm not sure if I kinked the fuel line, or over did it with the float height, or if fixing the float height got it "right" and threw the existing jetting out of whack. The thing starts first kick with no choke on an 18 degree day (literally), so I think it is REALLY rich. Ill pull it back apart and see what jet is in there, back off the floats a few mm (I probaly moved the float height 7mm just to get it in spec) and pick up a few leaner slow and main jets and tune it on the trail.
Anyway, when you have the carbs out, check your float height. Mine was *way* off, and fixing it made things much better (no more drooling, and running better).