OK, think I have a handle on it now. I got a good run with the LS needle open one full turn, and the HS closed 1-1/2 turns, from the factory settings. Still needs a little tweaking, but it's flyable now.
I'm at 5000 feet, which would account for some of the HS change, but I've never seen an engine go that far from factory nominal before. Maybe the factory muffler was changed after the default settings were determined, in favor of one with more back pressure.
Thanks all for the help.