for those interested in the evo maf, this is the best fitting air filter adapter:
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I've tried 3, the spectre, which fits well, but is slightly too long to fit my big k&n filter, and I tried this one:
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The 2nd ebay one required grinding to fit the maf, other than that it is okay. The first one has a nice smooth entry for the maf from the top two sections. I'm using K&N RF-1008, which is the largest filter I think you can fit. It may not fit if you still have abs, it is very tight.