Another piece to this puzzle is that the VTEC high-output cams (AKA, the less FE cams) kick in at 3500 RPM. They will also kick in at lower RPM's if you press the gas hard enough, but they always kick in @ 3500 and above. So, for the most fuel-efficient acceleration phase, you'll want to keep the RPM's below 3500, and the optimal point is probably even lower.