Debateable I guess Airbox is big enough to supply the 900/1000 with enough air to make 85-95bhp with standard restrictive filter and makes for a good Plenum Chamber, upgrading to a race filter can only improve things. Most restrictive part of the standard box is the lid which is easily disposed of. i have seen plenty of bikes running a standard airbox, race filter and no lid making the Class limit on BHP. Some airboxes get cut to seperate the Battery and Electrics so they don't have to be removed everytime you want to work on the carbs or the throttle bodies
Thank you great info. I was going to just take the lid off but it also made good power on the dyno with the lid on and a k and n. Just for info had it done at the dyno centre. It's run by ex bsb racer Stuart Nicholson and great value for money. Well I thought so!! 01609 760466