The Scion tC factory exhaust is not really designed with optimum flow in mine and more toward easy of fit and mass reproduction. You probably already knew this if you have taken a look at the stock system first hand. We know you want to fix this poorly designed "T" shaped Scion tC exhaust system with a high flow quality unit to dramatically increase gas flow so we have given you plenty of options. Our Scion tC exhaust systems will increase horse power and torque while improving the over muffled exhaust note so you can hear that 2AZ-FE motor do what it does best.