Well, I"m not really up on all the ins-and-outs of tuning the UCE, but it does sound like an ECU related issue to me. But not necessarily the programming.
It might be running lean at the larger throttle openings, or it might be over-retarding the ignition timing for added load at the larger throttle openings, either one possibly causing power loss.
I don't know what may be possible to change in the programming of the ECU.
My experience with computer control systems is that if the program is running then the most likely cause of malfunctions lies in the sensors or the actuators.
Maybe there are some sensor calibration issues.
For your friend with the carburetor, I'd try a larger main jet, and possibly a larger needle jet and see if that does anything.
As far as timing, I have no idea what the UCE static times at.
But, 5 degrees BTDC would not be a terribly unusual static timing number.