Running Rich?

ill toss out the obvious: check cold/warm values of a few sensors. i would check the ECT, ACT and lambdas. you can pull codes too.
however, if one of these sensors is out of calibration, it wont necessarily toss a code, though it may be reading incorrectly for the situation (i.e. your ECT is telling the puter your car is cold, when it is running at 190*. the sensor is not out of allowable range, but incorrect for the situation).

what temps are you runnin at? IIRC, you gotta keep it over 170* (178*, i think) to be in closed loop.
good luck.