The Yamaha-designed Normally-Aspirated (N/A) 2ZZ-GE motor is the perfect bike engine - good horsepower peaking near the top of the rev-range with poor torque.
The factory manifold (header) is a poor design. A short, small-bore primary set feeding a large-bore secondary pipe - fit for a shopping car but not for a mid-engine sportscar.
On this 2bular 4-2-1 manifold, designed purely for racecars, I needed to increase power AND torque and that requires a completely different design. With longer, bigger-bore primaries and matched-length secondaries, there is no room for a Catalyser unless it's placed in the silencer.
It has all the features you'd expect from a Race manifold. Proper, merged collectors to maximise gas-flow and minimise turbulence, with a slip-on secondary section and V-Banded link-pipe to the silencer. All TIG-welded for strength and integrity.