I have a 2002 WS6 and I just recently installed new front O2 sensors (200 miles ago). I used Denso Corvette rears. My car was hooked up to HPtuners and, at idle, my O2's were switching but only maxing out around 700. Only when around 1200rpms were applied did the O2's jump up to the 900 ballpark.
Any ideas what could be causing both O2's to act this way??