Well fellas, an update.
You may remember, but a while ago I bought a new MAF for my S3, from GSF. But I decided not to fit it, as I don't think the existing MAF is the cause of this Hesitation, loss-of-power problem. The existing MAF meets the flow spec at idle, and in a 3rd gear pull to the red line, flows about 185-190g/s.
Anyway, over the weekend I decided to fit the new MAF, just to rule out that the old one is the cause of the problem.
Result. Today is day-2 of running with the brand new MAF, and the hesitation is most definitely still there.
Hesitation occurred twice this morning, once in 4th gear and 5000rpm, part-throttle load. Second instance, was in 6th gear, 4000rpm, again part-throttle.
What's next I do not know.
AL