My box as aluminum as well and is sealed also with two 3 inch hoses running to the front of the car. The only difference might be the size of the filter which I am running a K&N on the end of my CAI.
Dynoing bicycles? I think you need to bring it over to a real dyno. just kidding
Is your dyno one of those that has the two smaller rollers that the cars tires sit between when you run it?
And weather you have a box or just running tubes into your factory airbox. ram air is ram air.