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And if you was too add a performance filter to a completley standard engine....99% of the time you will actually lose BHP's.



I don't think that that would be true, I may be wrong tho.

Like I said before, the extra air intake from a performance panel filter will be so small in volume that the standard exhaust will be able to cope, certainly on most cars. I would imagine that all car manufacturers will build in an overhead into the capability of the exhuast, to take into account things like air temperature. (Due to thermal expansion, the cylinder will hold a smaller mass of air/fuel mixture if the temperature of the mixture is hot). Again like I said before, volumetric efficiency will only have an effect when the intake is vastly improved to bring in more air, certainly if you were to put a turbo on it DanST! But also to make the best out of significant increase in intake ability, such as a manifold, a modification to the exhuast would probalby be wise.