Wait, you wrote,
Well, it does have the dreaded hesitation problem between 3500-4500 RPM and it occasionally goes into the on-off mode when it comes to throttle position - cresting a hill and back off slightly to hold speed, and the throttle just shuts down completly then pops back on when I push down a little
You get that too? I sometimes get a feeling like the red line limiter kicked in around 2000RPM on 2nd/3rd gear. Or, more like fuel filter got clogged up. But, if I let go the gas and step on it again, it goes away instantly. Like I said, put some dry gas in it and see what happens. You may have moisture in the gas line.