How much of a gain results from a decent case matching process. I'm assuming you gain a fair amount of performance from the whole ordeal and I understand that it makes the fuel flow like it should to the ports and to the cylinder. But how much of a speed gain would likely result?
And also I have the same question for going from an open but unrestricted pipe to an expansion pipe.
And why does an expansion pipe cause a bottom end/full power band gain?