Some say the K&N does not perform well, others the opposite. You will not need a tune with just an air filter, once you change the A/F ratio by adding an exhaust, etc. you will benefit more from a custom map and a programmer like a PCIII.
I have a BMC in my '05 GIXXER 1K and my brother has the K&N in his '06 GIXXER 1K (both also have aftermarket pipes). There doesn't seem to be any adverse effect from either. I think you would probably need remapping if you put on a full exhaust system, but they seem to adjust very well to a filter/pipe combo..
Moderator Lifetime Gold Supporting Member '07 Rally Veteran
Join Date: Oct 2004
Location: Western N.C. (The Great Smoky Mountains)
to TWF rydin dirty and r1hooligan
I'm still on the oem filter with my 05 1K. The BMC is here awaiting the bikes next service. (In the next week or so) After that, Its on its way to the dyno to actually see which filter performs better. I was told to run the BMC or K&N with fresh oil for at least 500 miles to dry the oil a bit. Then bring both filters in for dyno run. I'm really curious how they compare.