will a k&n style cone air filter be any better for performance in any way then fitting an upgraded panel filter in the standard air box i have a pipercross panel filter in the air box at the minute. i have been told to get a decent cone filter but i don't know if its worth it??

 

Only a flow test can answer this. I was going to originally say the panel filter by far since the airbox pulls in cooler air.

 

In my experience, cone filter for the t5 sucks in hot air and bogged me down under acceleration on a hot day. My kn panel has been way better since.

 

Stick to the normal filter. Really no benefit to installing a cone filter unless you plan to do a full cold air intake, and even then the improvement will be minimal if any (same applies for an "upgraded" panel filter for that matter). Don't buy into the hype of all these air filter "upgrades". Realistically, the only real benefit of them is that they are reusable and will save you money in the long run (depending on how often you replace your air filter that is).

If you decide to upgrade, go with a dry filter like AEM Dryflow or equivalent. Green Filters are pretty good as well (Green Filter USA - Official Site) and are made in the USA (semi local for me actually ) but I do not know the availability for the 850.