Straight design without catalyzer = Power Up, because of the low exhaust pressure.
(Complied for Step-up tuning.)
The main part for the high output is the exhaust manifold shown on the right graph.
We recommend having a total full straight exhaust tuning by having more power by changing the muffler and exhaust manifold and tune the sound with the front pipe.
* If the exhaust manifold is changed, the engine check light might be turn on for a certain combination. So the muffler + front pipe combination is an effective choice.