It's totally unnecessary and you would have to go down to a very small diameter pipe to maintain some backpressure, which the H6 needs to produce bottom end torque. Plus, putting all the exhaust pulses into the same pipe produces a scavenger effect that helps to "pull" the following pulses out of the cylinder. That's why on race cars, etc, builders spend a lot of time in R&D on tuning exhaust headers to find the most efficient means of evacuating the cylinder of exhaust. Wide open big pipe doesn't necessarily mean its efficient at all the things that the exhaust gasses are doing.
Last edited by GTEASER; 12-09-2014 at 05:20 PM..