The points are:

1) You do not get any extra performance w/ a different intake if you do not have other mods. For up to 500 RWHP, the OEM air system is more than sufficient in air supply. Do some searches and you will find actual references where you can read the study results yourself. Do not get your air filter at AMSOIL - plenty of OEM places to get them so that you can be sure they filter as designed.

2) The dealership told you the aftermarket intake is causing your problems - believe them! The oil on the K&N filter is a problem with sensors. The K&N does not filter as well so you get sticking vanes in your turbo (dust, moisture, etc). This can and, more often than not, causes over boost and head gasket problems (and warped heads).

"Stock" definitely means no aftermarket air intakes.