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.
It doesn't help. In fact, like stated, it will render your evac system completely useless. IMO they are basically useless anyway. Our vacuum pump pulls 19" of vacuum. All VP's are not created equal.
