Good Question! I agree with you that if the lid to air horn doesn't change, there wouldn't be any greater space to allow air through. But if the original filter housing lid was lower, then replaced with a drop base and the new one had a greater area between the carb and the lid, then obviously there should be a gain. And having a larger filter (in theory) should provide more surface area and slower airspeeds per cu.in. and give greater run times.

My 2 cents anyways!