I have a similar "click" in my car on startups when cold. A friend told me it is the ac-compressor switching on/off for some reason even if it´s not activated (It´s mostly is in "window-mode" when it happens). Does it affect rpm a little that corrects quickly when i happens?
Found out a few things.
-1st tick starts at about 130-135*
-about minute intervals between ticks, until car gets close to operating temp
-shorter, quieter ticks about 30 sec or so apart
-once car is completely warm it goes away.
I may sound like a dick saying this but... I wouldn't worry about the noise that much it doesn't sound all that bad and doesn't occur all that often. Drive the piss out of the thing and if it gets worse then you can worry about a tare down later i guess. These engines are noisy as hell, if i worries about every noise my car makes i would never get a chance to drive the thing and it doesn't even have 25k on it. My injectors are noisy as hell but i don't want to waste money on em cause im thinking of upgrading soon.