Originally Posted by VVG
This may also have to do with the proximity of the MAF sensor to the filter. I ran a K&N on my 2004 350Z for 14000 miles with no issue whatsoever, however the Z has a long intake tube and the MAF was around a bend in the tube so it may have been shielded from oil deposits. In any case, shouldn't be an issue in the M3.
I ran a K&N on my '03 350Z for over 50k miles and had no issues. One time, I even oiled it to the point where the filter oil pooled in the air box. Not the slightest hint of an issue.