is a k and n filter worth buying, any noticeable difference ?

[darrsi]

Personally I think the only place you'll notice a difference is in your wallet

Yes, if you do a lot of miles, you'll eventually break even with a K&N over eg a HiFiltro pattern replacement, but the difference is marginal.

Explain that one please?
It's simple maths that you will save money with a K&N.
I would've changed my paper air filter every couple of years, so I've certainly saved money.
They work well with these bikes too as they already run a bit rich so the extra airflow is welcomed.