In the MR2 community, a heated debate is going on right now about aftermarket exhaust manifolds (equal length, tubular, etc) are a waste of money.
The argument is the length of an aftermarket manifold acts as a small radiator, cooling off the exhaust gasses (whereas hotter gasses move faster, translating into more power, etc).
The counter-argument is that tubular, equal length manifolds pump exhaust gasses in a more equal, evened out pattern resulting in noticable advances in spool time.
What do you guys think?