Hello there guys...as you might be aware its been a month now (since i changed oil and filter at 26600km)that my car makes a cold startup noise after two or three days of garage sitting...(for half second until oil pressure goes up)i changed again oil at 28000km in case there was something wrong with it,noise dissapeared for some days...but here it was again...So I started thinking any reason and examined very carefully oil filter...Porsche OEM oil filter includes only one rubber sealing ring (large one 996 107 313 51) and does not include small O ring (999 707 465 40)...i removed oil filter cap and saw O ring damaged at one side...I replaced it with a new one and the engine starts up and at no time oil builds up pressure...finally there is no cold start up noise...So beware and when you change your oil and filter,always ask your dealer to replace small O ring at oil filter housing...Mine was not changed and so it failed...MAN filter includes O ring while OEM does not...!!!