Update
URD had originally sent me the incorrect wiring diagram for my truck, so there was NO connection to the O2 sensor at all to make the closed loop enrichment feature work. I emailed URD and Gadget replied with a different wiring diagram for my model year truck, one diagram is for a 2000 model year with California emissions that *taps* the AFR sensor in the newer trucks, and another wiring diagram for the 2000 federal emissions model (mine) that *intercepts and modifies* the O2 sensor signal. When I say "taps" vs "intercepts," what I mean is the Cali version has one tap connection to the AFR sensor whereas the Fed Emissions version requires you cut the factory O2 wire and run that signal into the URD piggyback and back out to the factory ECU...i.e. 2 connections vs 1 connection on an AFR truck. I made that connection this weekend and now the AFRs drop to around 12.5:1 whenever boost exceeds 3 psi in closed loop (where it used to stay at 14.7:1 until open loop).

I have more tuning to do but need to wait for this to arrive:

I can't plug the serial cable into the URD ECU when it's in its mounted position due to space constraints, so this little piece will no longer require pulling the stereo bezel everytime I want to make an adjustment. More later.