[DanG]

My first inclination is to pull the chip and see if the problem still persists. It's along the lines of a computer problem- Pull out a candidate for a bad piece of hardware, and if the problem goes away, you know what you pulled is bad. What kind of chip, where'd you get it, and how was it programmed (dyno tune w/ wideband O2, or just a pre-programmed "best guess" program)?

I hesitate to say the MAF is bad, but you can clean the MAF element with some electronics cleaner. Try swapping MAFs with someone in your area (or buy one from a boneyard to have a spare on hand). Make sure the MAF is from a car with the same fuel system as yours (return or returnless). The two are not interchangable in my experience, despite others' assertations to the contrary.