Since the FJR has been available State side for 3 model years I doubt that there are many things that *haven't* been tried. For better or worse, accidental and intentional.
Cost power? Not from my long-term experience. I've been running a K&N in two different FJRs for the past 50,000 combined miles now..... no, I haven't dyno'ed it, and don't need to: the bike runs no different whatsoever with the K&N filter installed; no more power, no less power.
One of the reasons for the inconsistant results is probably due to the fact that the filters, after being cleaned or on initial use, were incorrectly oiled. Not enough oil and, while achieving good air flow, you're losing filtering capability. Too much oil and you're causing too much restriction.
While I don't have motorcycle evidence I do have cage evidence. I have time slips from New England Dragway where we ran a series of tests that included air filter swaps. Converting from a flat box type paper filter to a K&N cone did make a small positive difference. We added a high flow exhaust and it made a huge difference. After adding the high flow exhaust with H pipe, putting a paper filter back in produced notably and repeatable less power. But, a big lazy V-8 responds to the little things much better than a highly evolved factory motorcycle engine, say something like an FJR1300. B)
@radman,
