You guys may want to check this out. This dude may have inadvertently solved this problem. Would be good if so.
His original problem stated (hesitation sputtering, but clears after 3000rpm):
Hesitation, sputtering, peice of Crap.
Here's the fix just posted tonight:
Hesitation, sputtering, peice of Crap.
So I'm gonna ask him which piston. Have ya'll inspected your pistons thoroughly already? I haven't checked your list in a while.