MAF! Maybe crazy coming from a guy with a Zetec, but mine did the VERY same thing and it took replacing the MAF to get the power back. Quick check...pull the MAF off the car and look at the posts. If it is dirty looking, get some Chemtool B-12 and spray it. May be time to just replace it.
What can happen is that the MAF can get dirty enuff to make it get out of calibration and thus change the mixture...when mine went bad, twice, it did not CEL so, that is a thought.
trying to help
Rich
