ok, so all this is in the other thread but...
I fitted a sprint08, a few months later I went to clean it, dust/pollen in the airbox. Cleaned all that, checked on forums, found a fitting issue - it bends on the side when inserting.
My solution to that was use a water based lubricant on the edges to aid insertion
So no bends, clean filter, clean airbox. About 6 weeks later I checked it again, same amount of pollen/dust.
So I bought a K&N, threw the Sprint in the bin.
I checked the K&N and airbox again recently, a clean airbox is the result.
 we're in a severe drought down here (as usual), so lots of dust everywhere.