I can't say how old any of the 3 MAFs I have are - they all came with the car. I wonder if as they age the element/resistor thingy becomes less sensitive (regardless of how much MAF cleaner you use), and they slowly lean out the car.
I'll buy a new one soonish, but for now I actually fixed the random cutouts by removing the rubber seal on top of the MAF, prizing off the cover, and then it was simply one of the socket connections internally had a dry solder joint!
I followed this guide I found on the SVX forums (our early TTs share the blue MAF with the SVX)