It could have been over-oiled when you purchased the filter, so the MAF could still be getting oil spray during suction. The thing I hate about oiled filters is that they get "better" filtering once they accumulate some dirt. What this means is that until they get to a certain threshold of dirt impregnation, the filter is not actually filtering out the debris as efficiently as it should. What tends to happen is that they rely on the oil in the filter to trap debris, but that oil has nothing else to bind to so it ends up sucking into the engine....and the MAF is directly in the flow of the oil.
Best thing you can do, if you want a "performance" filter is just get a higher flowing Purolator (OEM style) filter, or find a dry flow filter (Amsoil). Avoid oiled filters at all cost.
2004 Ford Ranger 4x4 XLT.....4.0 V6....4.10 rear
2" torsion key crank
235/85/16 Goodyear Duratracs
Gibson exhaust (POR20 coated)
Last edited by web; 11-23-2012 at 05:23 AM.
Reason: Updated test