Replaced petcock, fuel line from tank to carb, and inline fuel filter. All those things helped. To be honest though... I think it needed *even more* gas in the tank. I realized the tank had been lined with something to protect the fiberglass from the ethanol. Which is great! But it gives the interior of the tank and bumpy and uneven inner topography. So I think it needs a pretty full tank in order to get full fuel delivery especially on a steep incline.
Regardless, it is very peppy going UP the dirt road now. Descending a steep hill I experienced the sudden drop in idle that you mentioned @feetupfun - if I was doing more serious rides on a frequent basis, I would probably look into replacing the carb, but for now I will just keep it original.
Thanks for the tips.