Tomei introduced the high efficiency 4-1 as against the STD 4-2-1. The exhaust efficiency of the standard exhaust manifold is not perfect, but Tomei 4-1 type exhaust manifold has high efficiency. You could see the change of dramatically driving feeling.
The complete equal length is good for the exhaust intervention but reduce the turbine performance and increase the exhaust resistance. Contrary to that, the not-equal length exhaust manifold can lead the efficiency of other cylinders. Tomei design the not-equal length.
These exhaust manifolds make for an excellent upgrade because they save weight, and are designed with less restriction to improve the power and performance. This manifold is perfect for those of you on the quest to make more horsepower, more torque, and to really get that flagship flat-four sound.
High-efficiency 4-1 type
Not equal-length design
Great expansion of bore size of support pipe
Dry racing sound
Lightweight and rust-proof
SUS 304 stainless steel materials
Comes with new gaskets, hardware, exhaust wrap, and stainless steel zip ties take this manifold ready for the installation