K&N Filters - Are they good?

[<tsperez@xxxxxxxxxxxxxxxxxxxxx>]

OK, I have a simple question.  Is there scientific proof that a K&N air
filter improves performance in a basically normal (unmodified) engine?
What about in an engine that has been chipped with a plain over the counter
performance chip?

TIA,
Tomas S. Perez
tsperez@domain.elided
94 540i (K&N still in a box and no mods (yet))
93 325is (with K&N only)
89 535i (with K&N and chip)

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