ok mate. so with a drilled airbox, what difference would one of these make? Cos if im gonna drill my airbox I will get one if it doesnt make much different I wont bother drilling either. I mean as in Sound difference
For the C I have heard good things about the pipercross air filter, shame you have already bought the K&N or I would of recommended the pipercross. However the K&N should still do the job.
As for the drilled airbox, a few people on here have done it and I havent heard any complaints; have a look at dearings airbox as he has run an extra cold air feed to the drilled bit, which really is the only way you will get gains from drilling instead of just a nice sound.