This weekend I connected the Nick Williams 102 throttle body to my 2002 Corvette to look at how it fails.
At about 15% throttle opening, the blade starts to oscillate. My first thought was that this was due to the PID gains being too high, but it could also be due to to the higher current consumption causing the TAC module to cut power (which leads to no current consumption, which restores power, and the cycle repeats). If it was just PID gains, I'd expect the blade to continue opening as it oscillated, but it acted like there was a hard stop at 15%, so I lean toward the over-current protection theory.
Like a fool, I neglected to note the ODBD2 fault codes that came up when this happened. I'll do that next time.
To see the video, go to the files section, and look for the NW102_Oscillation.mp4 file. I tried to slowly open the throttle to about 50%, but you'll see the blade stop advancing and start fluttering. That happens twice, then I just stomped full throttle and the results were only slightly different - slightly more opening angle (due to momentum?), then oscillation, then an abrupt close as the car went into failsafe (with "reduced engine power" displayed on the dashboard).
If it is over-current, then a less stuff spring might fix it. Or perhaps an additional output transistor in parallel with whatever is providing current now.