Where did you get that info from? I can't see the rev-up weighing 90kg (~6%) more than the non?
My350z website, that weight is over the entire car, not just the engine, sorry, badly worded on my behalf!
I realised it wasn't just the engine you were talking about... It'd have to be made of iron or lead for just the engine to be 90Kg more!
I'm sure those figures are correct for the American cars, but I just don't buy it for the UK spec? They are basically the same car with the same engine... Only very small changes were made like a few things in the interior. I have no evidence to the contrary, but I just can't see what would make the car so much heavier?