I just went through the o2 sensor thing yesterday. I copied my performance tune tables (based on 20050) into a 20228 base tune per
@HansO 's suggestion. I forgot to uncheck the o2 box. To make a long story short after you uncheck the o2 you have to download the tune again. According to Hans the later tunes have improvements to the idle programming that isn't accessible with tuning software. Seems to be the case. Mine drops right back to idle speed now without the little hang around 1200 rpm. It also starts and goes right to idle speed without going up and then back down which I never liked. We'll see if it stays that way or "adapts" it's self back to the way it was. Fingers crossed it stays like it is.
P.S. thanks for the help Hans !