:The lower manifold being too small implies that you believe porting the manifold is a big benefit?
:I'd be really surprised if the plenum and throttle bodies are sized for the NA since it doesn't flow as much air. What makes you think so?Although I haven't measured the flow difference, I always port match the lower plenum to the heads on a performance rebuild. This isn't required on an NA, because the ports between the lower plenum and head pretty much match. Nissan purposely built in some restrictions to keep the power output at less than 300 HP. The stock exhaust manifolds are a prime example of this. Because people have seen gains with upgraded throttle bodies at low power levels tells me that the throttle body is a bottle neck. The plenum is sized rather small, and the runners are too long compared to most dedicated forced induction engines. The runners in the GTR, for example, are much shorter than those of the VG30DETT.
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