This one was asked for by David from Oz as I have commented a few times on how I have modified my breather setup to reduce oil-loss through the breather, as the set of pistons I currently run actually already have a bit of blow-by at high rpms (over 7k).
As you can see (unlike stock) I use a long tube that goes over the back of the frame and down into a breather filter. The step rise is there to have the condensed oil run back into the engine, whereas the water vapour will just be blown out. The same system (and inspiration) can be seen on old Guzzis, Yamaha SRs/XTs (that's where I go the idea from) and old classic superbike Kawa Zeds and Suzuki GS thous. Which also somewhat means there has to be a grain of truth in it...
This is by NO MEANS a branded filter, but it doesn't have to be. It's surface is a multitude of the cross-sectional area of the breather tube, so even if it might not flow as well as a K&N or any other branded filter, it will EASILY be good enough. And honestly, the filter is only meant to prevent dirt from getting into the engine, so it doesn't have to do much really.
I hope this answers all the breather-related questions, if you still have any or noticed other mods that you absolutely want to see a post about, let me know via mail or just write a comment below and I see what I can do about it.