1NZ-FXE inake manifold ?

[Yaris Hilton]

When you go changing around manifolds, you're likely to change the resonant frequency at which you get the optimum "ram" effect of the intake pulsations producing a positive pressure at the intake valve near closing, which gives you a bit of free "supercharging." The stock engine with the stock manifold has its torque peak at 4200 RPM, but has an amazingly flat torque curve across the whole band. You might end up getting a higher peak, but lose torque in the midrange and lose performance overall.