When I fixed my phone il take pictures of my modified airbox and that has made a noticeable difference. Only at speed though as it's a forced air induction. It's added 15mph down a 1.1 mile straight where I live. Put my drill box on and then lost 20mph.
So from a standard airbox I loss 5mph with a drill box but with my modified airbox I gain 15mph over the standard airbox.
I doubt I would see a gain on a dyno as the car is stationary and not forcing air in at 100mph.