Cheers for those mate, I've already looked through the workshop manual almost front to back looking for clues. That section is handy, but is really quite vague as to what they mean by each sound...a 'tap' may be a 'knock' to other people!!
Considering there was (somewhere) a TSB about the fuel dampers making a knocking sound, and mine is pulsing...I think I may have found the cause?? I can't remember where I saw the TSB though!!
http://www.350z-tech.com/zwiki/Category:TSB
Haha, nice one mate...you're doing well tonight!! I can't find a mention of this in those TSBs.
Reading this thread linky, he does mention there was a TSB on it.
I'll keep searching!!
Did you manage find anything by any chance... i have the same noise