There's a 2 x 58mm throttle body, P/N 20360NOS. It's designed for the Chevrolet LT1 engine as used in the late model Camaro, Firebird. Internal nitrous passages can support 50-200 additional horsepower when on nitrous. Installation is simplified because it uses the factory TPS and IAC. Vacuum ports are provided for other hook-ups. This throttle body installs cleanly and there's no need to modify the air inlet ducts!