Does any OEM company make engine air filters for 06 HiHy? Fram didn't have one in their parts catalog (at least at Wal-Mart). I tried an air filter for regular Highlanders, but it's a little too tall. Will I be forced to go to the Toyota dealer and get a filter, and if so, how much do they charge?

I don't know if anyone but Denso (Toyota OEM) makes them. It should cost around $23 for the part.

K&n makes one -- $49

Does anyone have any data that shows that the K&N filter helps get any better mileage in the RX400h or Highlander? In my last two cars I had K&N filters and the claim was increased HP. But I also changed out the air filter housings for increased air low.

I would change out the filter (in the stock housing) if it helps, here is the http://www.knfilters.com/search/prod...x?Prod=33-2344

No data but I'm sure it's marginal at best. If you think about it, the engine would have to "want" the increased air to mix with the increased fuel flow under hard acceleration.
I say get it if you want it. The K&N's don't dirty the engine oil enough to necessitate more frequent change intervals than the already accelerated intervals for cars in America.

agreed. clean paper filter will flow whatever the engine requests. should be a negligible to non-existant hp or fe gain. the k&n is nice since it will flow for a long time & won't get clogged as fast as the paper. also, it's a lifetime filter with a cleaning/re-oil every 50K or so. just be careful not to overoil as that could destroy the maf sensor element - a problem that plagues the vw/bosch maf's (my other car is a vw). i would suspect our maf is of better quality.