Invidia | Catted Test Pipe (350Z HR, 370Z, G37)Invidia 370Z Test Pipe Kit (HR Engines only. Also suits 350Z HR) DOES NOT FIT DE ENGINES. View this listing for the DE model. The factory exhaust will always have restrictions and these restrictions are normally highest near where the catalytic converter is found. The Invidia 370Z Test Pipe Kit uses a larger pipe diameter and smooth bends which allows exhaust gases to pass with fewer restrictions and turbulence. A High Flow catalytic converter is then