When it is exhibiting the symptoms, unplug the Mass Air Flow sensor and see it it runs better- this reverts it to a "mapped" input in the ECM instead of relying on the MAF signal. The EPC, CEL, and ASR (assisted steering response) lights all come on because this deals with torque distribution (working together with the ECM, ABS, and TCM- if you have an auto trans)
If it runs better replace the MAF
Thanks for trying but I actually tried that on my own with no change.
Ok- so other things that can cause a "low input" at the MAF are that there is an unmetered air leak after the MAF somewhere- vacuum lines are most common, but also the rubber hoses in the PCV system (under the intake manifold, and the "Y" pipe at the end of the valve cover. The "vacuum amplifier" under the intake manifold also tends toget clogged up, it is a black plastic cylinder with a rubber hose from each end (one end to the underside of the intake manifold), and one more at an angle from the middle.
Worse case scenarios are that you have a wiring issue (will need to overlay the wires from the ECM to the MAF, I have had to do this a few times so far this year) or that you actually have a bad ECM (highly unlikely, more likely to be the wiring