Quote: they don't work well with exhaust pipes and mufflers.
Really? I would have thought that a well designed exhaust system with x/h pipe would actually help due to a greater vacuum created by the extra exhaust pulses compared to open headers that only see one bank of cylinders.
In all my testing of the evac systems, the most I could produce was 5"hg and if you run a exhaust system that has ANY back pressure it will reduce the effect of the evac by the same number as the back pressure, in other words, if your exhaust has 2" hg back pressure it will reduce the evac by that amount 5"- 2" = 3" and if the exhaust system is greater than 5" hg it will back up and burn out the check valve at the collector and start to pressurize the crank case
