[Jake Raby]

This noise is coming from looseness in the timing chains due to the hydraulic tensioners.

Clean or replace the tensioners or change oil brands. One brand of oil made the noise completely disappear in my Wife's 996 Land Speed car, when I changed brands again the noise returned.

Wear on components like variocam wear pads, timing chains, cam drives and etc will make the noise louder and occur more often. There are solutions, you don't have to live with it and it isn't good for the engine.