which is the best air filter

[jasengine]

I have the standard paper filter. No point having a performance type on the a diesel, even a tuned one. I had an oiled cotton filter and then changed to a standard paper type and felt NO DIFFERENCE WHAT SO EVER.
The oiled one do not filter out all the dust: I found a very thin film of ultra fine dust in the intake pipe from the air box and I cleaned and re-oiled the filter every year!