I have never diven a RB core version so i cant comment sorry bud.

When the turbo gains full boost depends on loads of things like cams and mapping etc. I had full boost with mine just before 4k rpm but only reving to 7.2k, thats a very old skool T4 and Greys set up.

Other T4 cars wont get full boost till 4.5k but rev to 8k. Like i said it depends on spec really.