Larger engines require more air, simple as that. The upgrade for the original 61mm turbo is this 76mm wheel from Turbonetics. It has a ball bearing, 0.96 A/R ratio, and a T4 flange. We upgraded the blow-off valve (BOV) with a compact version from Turbosmart. In the past, we’ve had problems with small BOVs failing to vent boost on decel and blowing off the intake piping.