Clean air filter could add 5hp!

[Jug]

I think it is the airbox mainly, either bad design or just not a large enough filter area, either way it's a known issue with the 990 of whatever flavour.
I have seen some pictures of DIY modifications, cutting rectangles in the airbox lid and installing additional filters.

My mate has just changed the air filter in his VFR800 Vtec after 30,000 miles.
It looked like this.

old & new.jpg

He was hoping for a noticeable improvement, non was noticed...
No doubt there will be some power increase but realistically how much do you need for it to be noticeable?
I can't explain the gains shown in that video but that old "dirty" air filter didn't look that dirty to me, not compared to my mates above.