I'm not saying i-VTEC doesn't help, I'm saying that the dominant factor is displacement, not intake timing. Also, the engines I'm pointing to with large gains over stock intakes are all 2.5 L or above. I'd also say that a K20 without i-VTEC would probably still have more gains than an F20 because it runs at higher RPM's, so it demands more air and has more benefits from an intake.