Air filters

[danielc3009]

Hi

I'm looking for some advice about air filters

How offen do you recommend replacing them with new ones? I'm changing mine after every race day and clean it and re-oiling it. How many time can I be used before I need to replace it?

I've got a 2 stage filter and there's some dirt stuck in the outer foam. There's not much but I can't get it out no matter how I clean it. The inner foam is like new, should I worry about it?

Also what filter elements do you recommend.

Thanks