Boost is 0.8 - 0.9 Bar, 11.60304 - 13.05342 PSI, this is what the specs say for the 4wd, the 2wd run 0.7 bar, 10.15266 psi.
As a rough rule stage 1 is around 14 psi, nearly 1 bar(1 bar = 14.5038psi), a stage 3 can run with std turbo and dark greens 0 280 150 803 injectors, but turbo will be limting factor for bhp.
As for the sound are you runing a std airbox now but a cone filter before on the 2wd ?
Exhausts have got quieter due to legislation though as theyears gone by, maybe the
2wd was a older system ?
tabetha