Just to play devil's advocate @rich83...
My car made 270 with just a full BCS (sport cat) and Pipercross panel down at Hinckley.
Could it have made 10bhp more at peak with a well-flowing intake like a Ramair? Probably. I honestly doubt my Pipercross panel gave much more than a stock filter would.
There's also something worth considering with Seanie's map. If boost is tempered a bit at mid revs, say around 3k, it gives the turbo (mapper) a chance of producing a little more boost at higher revs. Mine made 345lb/ft of torque at 3200rpm, but dropped off a cliff soon after. This map makes considerably less torque at around 3k, but then holds on to the torque much better than mine.
So, it's maybe fairer to say that this car could indeed be making enough torque at high enough revs to make 280bhp peak power, at the expense of that good old k03 punch at low-mid revs.
It's also just as likely that this dyno, or any dyno for that matter, isn't entirely accurate
