Thanks all for reply,
it seemed to be VarioCam wear pads.
I have no trouble with the car and no suspecting noise. daily driver, mostly city driving.
As i search the forum, Jake Raby mentioned "easy driving"
http://986forum.com/forums/performance-technical-chat/51235-camshaft-deviation-analysis.html
I don't have durametic, so i will find a Indy shop and get it checked...
and will check the oil filter later...