Eish, you really read alot on the internet dont you........
Not alot of nissans locally had a VQ45, I think maybe 1 patrol did, importers wont sell you one off a working motor, sometimes you're lucky and they have a wrecked motor.
NOW.... for my 2c.....
The 80 - 90mm of a throttle body that size will be too much for a stockish setup, yes it will flow more at high rpm and you probably will gain a few KW, but you will loose alot of low down torque as the air will be stalling at low RPM and your throttle response will be terrible too.
THE ALTERNATIVE
As I'm such a helpful guy here is a nice alternative, the SR20DE throttle body will also bolt right on, you just need to extend a shaft for the TPS, a mate did this with a pipe and some pratley steel, this gives a nice compromise between the 2, also you can see if you can find a KA24 throttle body off a 2.4 hardbody, that fits too but I think its smaller than the SR one.