I've just taken the airbox trumpets off my otherwise standard 750ss and apart from the added growl it's also smoothed out the pickup of the engine coming onto the throttle. I can now open the throttle harder without it simply bogging down from a flood of petrol.
I've been checking the plugs since doing this and the engine seems to still be burning on a near perfect mixture going by the colour of the electrodes.
You probably all have modded airboxes and K&N filters anyway, and thus this is redundant as advice, but I thought I'd share my experience anyway.