Thanks for the info about checking the monitors.
I'm new to HP Tuners and OBDII stuff, I've had more time playing with OBDI and Tunerpro RT.

My Tahoe is at a shop getting the front diff bearings and seals done but as soon as I get it back I'll see if I can figure out the readiness monitors.
I have access to a friends Snap-on scanner, so I'd like to think it should be able provide the info I need.
The scanner (and YouTube) were great at helping track down a faulty FTP sensor that was throwing an EVAP P0446 DTC.

My interest in following this post will be if EGR doesn't work with the 12212156 O/S they've sent me I might be able to learn how to get both E-Fans & EGR working.