I have no idea on the numbers etc of the Borg ones, need someone to point me in the right direction.

I admit, i have been alittle vague lol.

My T4 is pretty much maxed out. Im changing a few other bits so thought i may aswell throw the turbo into the mix too.
Changing turbo to improve spool and to remove some of the stress, but if that gains me some horseys and torques then i shall not complain. Somewhere around the 550 figure sounds like a nice place to be, but from what i was aware, thats kind of putting any of the GT30s near their limits ???