Reduction of back-pressure in the exhaust system is the target for all supercharged exhausts.
The 2ZR-FE motor, as it comes from the factory, has an amazing 186ft/lbs of torque. If you use too large a diameter downpipe, you damage that figure.
The 100cell FIA Approved Race Cat increases power and torque by using a specific downpipe diameter to enhance the gas-speed.
2bular always uses a welded gasket cup for strength and good sealing at the OEM manifold.