Strange moment curve

[jondee86]

The exhaust will have harmonics that improve the scavenging at
certain rpm's. And the intake will have harmonics that improve the
cylinder filling at certain rpm's. Depending on where these "peaks"
occur in the rpm range, you will get better or worse torque.

Factory engineers will spend thousands of hours experimenting with
different designs on an engine dyno to balance the peaks and troughs.
When you design your own intake and exhaust, you take the chance
that you will have some different results (good or bad) from the
factory setup.

Cheers... jondee86