However, if that is the case, then while the O2s are still "warming" up I believe the car should run in open loop mode. In which case if you're getting hesitation it might be because you have a boost/vacuum leak somewhere. I tracked down and fixed a big boost leak in one recirc line. That helped noticeably, but mine still bogs a little when cold. It goes away after 1-2 minutes of easy driving.