OhSigma,
It depends on your type of forced induction...
If you are running a supercharger...These same rules apply, BUT if you are running a turbocharger, you have to relate the Crosses sectional area of your Turbine outlet to the size of your wastegate, and also the style and size of the Exhaust turbine... You see on a tubo application, the turbo itself acts as the restriction. What rara spoke of as far as scavneging does not really apply to a NON-N/A motor(but on a N/A motor scavenging is key to power gains). Ideally on a forced induction motor you want as little overlap in your cams as possible(intake vs. Exhaust) but I digress from the whole topic at hand...
Terry,
I agree with what you are saying and also what rara is saying, but I beleive that what alot of people are missing here is that the "restriction"that you want to impose should be at the "front" of the exhuast, IE the size of the Header tubing, not jsut some catback exhaust diameter(once you run into CAT backs as your imposed restriction for this test you'd also have to deal with cooling of the exhaust gases slowing velocities etc.. where as at the header these temps will remain VERY high compared to , lets say at the resonator... this would eleimate some of the variables that people will try to claim caused the drop etc..)(also,i know its cost restrictive to try differrent sizes, so we would have to go witht he fact that the ford guys got it right for most of our apps)In this instnace, larger diameter header tubing would definately slow the exhaust velocities, thus killing your torque, and power in general accross the power band. But too small of a header tubing and you would be horrendously starved for breathing. So as far as headers go, yes there is a fine line for restriciton vs torque.
Just another aside, If any of the supercharged guys had a crappola amount of money lying around, Id like to see a set of larger diameter headers with Velocity stacks at the exhaust ports on the heads to increase flow velocities into them.. i bet these would yield the biggest gains overall.
I think I strayed way off course on the topic here, forgive me.. I'm rambling
