Random thought. I have a '97, light came on a couple of years ago, with no apparant loss of performance. It stayed on for probably six months before my wife got a different car and I started driving the Lumina full-time.
One day, on open highway, I cranked her up to 85-90 mph for a few miles, and the light went out. It stayed out for several months, then reappeared. I repeated the drill, went out for a good hard flog, and after a couple of miles, light went out. This happened a couple more times, and each time the hard run cleared it, becoming less and less frequent, now it hasn't happened for some time. I always suspected it might be a code like yours, caused by injector fouling, but never had it read.
The wife's ZX2 started idling rough and SES came on a couple of months ago, So I tried it on that one. I didn't even get to the bottom of the entrance ramp, WOT, before the light went out. Hit the next exit, came to stop, idle is perfect.
The old "get it out and blow the carbon out" wisdom still has some merit, it seems. I think sometimes they just spend too much time in heavy traffic, and stop and go driving for things to clear out. Injectors and Catalytic convertors, O2 sensors and other things need to be run full flow and hot to burn off deposits, is my theory. At least, that's what I tell the cops.