Ian, here you go mate, all explained in this very thread we're chatting, direct link here:
http://www.350z-uk.com/topic/85194-investigation-pg18-mouthwashs-sssb/page__st__100#entry1327686
So, as you can see, you were there with us, I did show and explain to you what we were doing before Darren turned up with the fuel pump if you remember now. Also you can see fuel dampers where kept as we kept the OEM fuel rails while we only replaced the injectors.
Have you managed to find the printout from the shop that cleaned and refreshed them which was provided by Darren?
Also, do you remember about the oil we found when we've replaced your sparkplugs, it's in the photos above. You were mentioning having the rocker covers replaced at some stage. Perhaps that needs looking into now.
Please don't take this in any other way, I'm here for you as we've discussed in private from my own initiative. I would have loved to have a look at the car at no cost, of course, but you've never asked us to do it.
Anyway, let's hope it's a quick fix, try what Keyser mentioned above and also Sam, too.