Cold air intake

[The Radium King]

i think the issues with the aftermarket CAI are threefold:

1 - oiled filter. if over-oiled you can ruin your airflow sensor. been there, have first-hand experience with that.
2 - oiled filter. when first installed the oil does a good job of capturing particles, but with no oil, the openings in the filter are larger than on a standard filter, so, you've gone from a 'default safe' situation (oem filter will just block more particles as it ages and plugs-up) to 'default unsafe' (oiled filter will pass more particles as it ages). oiled filters were not originally designed for performance, but for recyclability, so make sure you keep you maintenance up.
3- cold air. engines are very sensitive to intake air temperature (iats - important enough that your engine has a sensor for it). the oem intake draws ALL air from outside the car. the aftermarket CAIs do not seal well against the side or top of the engine bay and, if you do a search here, you will find tests that show a significant increase in iats when running an aftermarket CAI because they draw in a significant amount of air from the hot engine bay (I think it was jake, but could be wrong). easy enough to test yourself; iat is one of the obd outputs that you can track with a cellphone app.