Update, been out today to try and test the airbox mods, only managed 30miles as the Derbyshire roads were too busy and lots of x-mas dawdlers
At road legal speeds it's difficult to feel a genuine difference, but it has stopped making the awful 'wheeze' when applying throttle in a high gear at low revs
It ran cooler, fan never cut in
And it now sounds superb, nice gurgle of induction
So for me it's a tick, but I will be working on a Naca duct to fit against the side louvre