With a properly working/designed wastegate system,,it will control the boost pressure.
But, like I stated earlier,that turbo is too small.
A Buick GN turbo would be a better choice over a Volvo turbo,& guys sell there stock units all the time & upgrade to a larger turbo.
I believe the Volvo turbine housing A/R is .48,thats small & the wheel is really small also. Can you say choke??
Realistically,you can run up to about 8 psi,but not w/the Volvo turbo, it would generate so much extra heat trying to feed the larger 4.1 liter engine it wold most likely detonate quite a bit unless you use methanol injection all the time.
http://www.alcohol-injection.com/ example
Also install one of these nice units.
http://www.jandssafeguard.com/ this unit will save your engine.
MBHD