finally i fitted the new maf i bought from a guy on here!! the original one on the car was a plastic one, but the one i bought was in fact a metal one!!! it fitted ok, and has cured the problem massively (stuttering when under-load), but not 100%! this i think is all to do with the metal one coming from an older V6, a 1997 i think, mine is a 2000 ST24 so i have what i think is the "refined V6"???
going to look for another maf, preferably a plastic one so the serial numbers on the actual sensor are actually the same and that should cure the problem altogether!!!
I dunno what problems, it's not necessarily simple when there are so many sensors and other factors like the age of the car and wear of the engine. Things like the lambda sensors or IACV could make it run badly, for example, as could ignition leads, the coilpack or a vacuum leak. Worn or clogged fuel injectors can cause poor running too, or a blocked cat!
As for serial numbers, I don't know what you'd be looking for there. Surely a part number is more relevant.
Hope you get it sorted anyway, maybe a plastic MAF would be a good starting point as they do come up for sale cheaply occasionally.