That certainly confirms that the TPS cannot be set at baseline through the ECU, but requires voltage measurement at the TPS itself.
Thanks, again, Camn!
Camn's observation is confirmed. While the voltages at idle are very similar (+/- 0.001 mV), at the 150mV baseline at the TPS through the Casper breakout harness and a DVOM, guzzidiag reads the throttle voltage 0.000.
I'm thinking a new "tune-up" thread is forthcoming based upon these new tools and developments.