Okay I got the new manifold fitted up. Total Runner length to the valve is roughly 16 in. I'm just adjusting to odds and ends right now to get everything working together correctly.
According to my figures they should peek out at around 6200 RPM. According to Auto Mafia racing, on the 3.7 with the turbocharger and slightly larger intake camshafts it is around 6,000 RPM for Peak.
About 2 inches shorter would be great for really revving out.
Why switch over to this particular manifold. Cuz the tune resonance allows more air flow at lower boost levels. So lower wastegate Duty cycle. One other thing to consider. Horsepower equals torque at RPM divided by 5252. The higher you Rev, the higher the horsepower. We are presently peaking out at around 5,000 rpm.
None of that actually really matters though. If you can hold torque production farther out in the Rev range. You can then raise the shift points. Gear ratios are torque multipliers. So the longer you can hold the lower gear ratio. The longer you're at the higher torque multiplication of that lower gear. This is all theoretical though until I get out to the track.
To get all this to work and fit in took a little bit of Ingenuity and careful selection of factory parts and other odds and ends.
Oh one more thing. These manifolds are only considered safe up to around 12 PSI. They are plastic.