I know that the MAF sensor plays a role but what is it. I am keen to get an induction kit so why is the MAF issue so important?

A M.A.F. is a "Mass Air Flow" sensor it controls the air fuel ratio of your engine depending on what its internal sensor tells the ECU what is going on
you can fit an induction kit on the end of it but be warned on MAF's with hot film sening rather that hot wire sensing some induction kits can be harmfull and cause pitting of the film leading to MAF failure usually STi 5 or above or my99 onwards.

Best advice fit a panel filter such as an ITG in the original air box unless you go the whole hog a fit a link in which case you can shove whatever you want on the end.

Regards

TKH