[MiracleMax]

Well, that depends really?

Its not as compromised as the production piece, so if all is good then its a net zero gain. However that said, The RPM is designed for a higher reving package so it isn't tuned to the RPM range at which your engine is designed to work.

You really have to ask yourself what you are planning on doing with the motor?

The performer RPM is designed for what? The 2500 to 6500 rpm range? Where as the performer is designed for off idle to 5500.

I say with a gear and the manifold any loss will be transparent.

You might want to consider this though, why not build a seperate engine. One that is designed to take advatage of the RPM manifold, then plop it in when you've got it ready. The money you spend on the RPM manifold will be pretty well spent in this case.