Well.. Oddly enough.. My noise has vanished again.. No logical reason I can come up with other then maybe something is broke in and sorted itself out.. Still kind of noisy on cold start up but every car is noisier when they are cold.
Received a package in the mail from camvap today. Very generic looking and gobs of paperwork to fill out, even after I already did it online already. Useless. I'm not going to push it further. I've still got 60,000km of warranty left and by that time if the noise gets worse, they will have to replace it later on.
As for the filter..
http://www.nissan.ca/content/dam/nis...n-micra-en.pdf
Steer them at that.
But judging by the way your dealer is treating you, sounds to me like you might have an 'abnormal normal engine noise' like I do.. Except for now mine should be called an "Intermittent abnormal normal engine noise." Or you might get the "I have brand new micras that make the exact same sound." out of them.