The simple fix is not to run any form of pod filter directly off the afm or any type of afm for that matter.

Z32 afm's aren't immune to oil contamination either, they just handle a bit more before they die.

ACA branded z32 afm's are the cheapest @ around $300.
Bosch boxed are around $350 (Modyourcar etc)
Z32 (Nissan boxed) through a dealer here is EXXY! (if it wasn't i'd have one for it's superior resolution).

There are also cheap chinese knock-off copies of z32's floating around:
Knock-off copy z32 info & pics

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[CENTER][COLOR=#ff0000]Built Ej207: Semi-closed RA Cases - Wiseco Forgies - Manley rods - BC 272 cams - GDA Heads - billet f/whl - Vi-pec - WbO2 - 800cc Yellow tops - TD05-20G - 409Hp ath @ 1.75bar on E85[/COLOR][/CENTER]