06 VW TDI air filter\housing

what is the purpose of oiling the air filter? what is a good dry AC for this car? If the flap under the AC is open when the engine is OFF (suppose to be closed) would this condition trigger an engine code? which one?

I am thinking that my MAF contamination issue is because of this. A light oily film was found on the MAF, triggered MAF codes. If I switch to a dry AC and check the flap for proper closing, this should fix the problem. Maybe I should buy a new AC housing unit? anything else to check? the MAF is fine itself.

The purpose of oiling the filter is to destroy your MAF; there's no other advantage. Do a search on "K&N filter" for more info.

The only way to test the MAF is logging output in VCDS. A quick test is to simply disconnect the MAF and see if performance 'feels' better. This of course will set yet another code.

A partially-open flap typically means it's bad, but will not set a code. The flap is located in the unfiltered portion of the airbox, so it's not a critical issue. Get your car scanned and go from there.

OK, thanks. so, a flap that is always open would not increase chances that the MAF might get contaminated? The MAF did have a slight oil film on it, the code was P0101. My question is how does this oil film get there? my guess is the air filter, not sure if it is a oiled one, though.

What kind of air filter is it? Remove the top of the filter housing and check out the filter itself. There will be a brand on it.

As stated by MyAvocation, the flap is on the dirty side of the filter so anything coming in through the flap is properly filtered.

I think it is OEM. Seems to dirtier where the flap is located under it. Sooty, black.

Buy a new OE filter or a filter from Mann & Hummel. They are the same.

You can keep the flap closed by placing a nut in the spring mechanism. It's probably not good for that flap to always be open.