going back a few years now the k&n filters were too heavily oiled and did indeed kill a maf with oil contamination. Obviously the problem became evident and then you saw all oil based filters being less saturated in oil. You can normally judge this by the plastic bag you will take the filter from upon purchase, if there is still oil swimming around in the bag then dont go near a car with a maf fitted. Nowadays most of the decent branded oil based filters are a lot cleaner so fine for most applications.
As said though, mafs fail on a regular basis anyway so you would be hard pushed to claim a filter has killed it.
Green cotton and itg seem to be the favourite filters at the moment for the vag car tuning brigade. itg are probably one of the only brands that can back up any power increase claims with induction kits/filters with any cinfidence, I have seen evidence first hand too (and NO I am not affiliiated with itg in any way ; ))
Most German manufactured turbo applications will have a standard air box and filter that will surpass any need that it is fitted too, regular stage 1 type tuning and the standard filter/air box will still be well within spec and cause no restriction to air flow.