Custom duals to y pipe

It's a common theory based on the premise(factual) that the gasses cool and shrink as they progress thru the system, the longer and more convoluted, the more the "heat exchanger" contracts the gasses. Go to Burns' exhaust site, They stated that any exhaust past 5' long costs power regardless of size design etc. The fact, from a performance standpoint, is that a longer system has a higher frictional factor that gets worse with higher velocities. Bigger is better. The "backpressure" myth has validity in some cases when the torque was boosted by the velocity in the system, or the A/F ratio changed in an unfavorable direction w/a big reduction.