Why would your turbo croak? Just because it is boosting 15-20psi? Is the needle spiking to 20 psi, then dropping to 15 psi... Or fluctuating between the two when your at WOT? And no, putting a bigger exhaust on your car does not increase boost pressure. All it does is free up power throughout your powerband and helps your turbo breath... especially in the upper part of your powerband.