The fouling up of the Air Mass Sensor is no longer attributed to aftermarket oil-based filters. It was initially thought to be but no longer apparently so. This is what I've been reading in the Porsche Club of America tech section where cars with or without aftermarket filters are also found with fouled AMS problem.
http://www.pca.org/tech/tech_qa_question.asp?id={ED1A5C64-0E4A-46E9-A655-44728DCEF9BF}
http://www.pca.org/tech/tech_qa_question.asp?id={594710AE-CB21-4DD9-B5ED-5B13027092EE}
My Evo intake just arrived and is pending installation
If I'm able to dyno my car, I'll revert on the results.
If you're worried about the EVO heat shield sucking in warm air, you can retain the original airbox and just replace the pipe to get rid of the resonance chamber which apparently causes turbulance to the intake charge.