K&N air filters add 5-10%? Also: xenon?

[Benjamin Weste Pearre]

1990 200TQA

In my quest for new headlights I ran across this:

http://www.audiquattroparts.com/tuneup/air_filters.htm

They claim that the K&N air filter will add 5-10% more HP to a car.
For my 1990 200TQ, they sell the normal filter for $10 and the
washable reusable magical one for $45.  Has anyone used these?  Do
they work as advertised?  How often do I need to wash them?  Washing
machine, or dryclean only?  :)

Also: say I get the Euro headlamps.  Do xenon bulbs really make a
great deal of difference over the some-other-halogen bulbs (xenon is a
halogen too)?  I've heard much about burning out H4 bulbs - do the
xenon ones last longer?  My alternator may not be up to supplying the
juice for 100W bulbs, so I'm looking for lower wattage brightness.
Can't I have a headlight made entirely from superbright LEDs that
draws 2 watts and spanks the DOT lights?

Cheers!
-Ben

--
bwpearre at alumni.princeton.edu                 http://hebb.mit.edu/~ben