RLF

I would say the only reason Ford fitted BOV's to our cars is to eliminate any possible customer complaints about flutter noise. There is plenty of people that would have no idea what the sound is and think that something is wrong with there car.

Boost increases air speed giving more volume hence higher volumetric efficency in the cylinder. They all relate to one another but for a high boost, high horse power application n/a airspeed is irrelevant. Bigger is better in a way, and that's when plenums are better suited.

If your looking for off boost torque and fuel economy down low your defeating the purpose of fitting a plenum to chase the big numbers up top. When there's boost in the runner I wouldn't imagine air speed matters, only flow?

I'm not totaly against plenums or anything, if my car somehow came without an inlet manifold I'd probly buy a plenum but why throw out something you already have that works good for basic setups, ie 300rwk. If I was to choose a custom plenum I'd probly go for something that holds a big volume, for some reason I imagine if it can over supply more volume than the cylinders require they should all draw in equal amounts at high rpm.

I think some people forget the engineering and very lengthy testing Ford have done themselves. The factory manifold might not look shiny but I bet it works a 100 times better than even some of the high end plenums available. Ford would have done hours of simulation testing before it even made itself onto a vehicle for real world testing. The xr6t engine may not be putting out 600hp standard but Ford have to warrant the engine for 3 years under some very extreme driving conditions. something to think about when tossing the factory item in the bin for joe bloe's performance plenum..