When I bought my bike, there were pod filters on it. Air box was long gone and did not come with the bike. I have gone through everything on the bike, tuned to perfection (or so I thought) I even switched to K&N brand pods I got for a great deal. I was happy. Then a little over a week I rode a friend's bike ('74 Cb750) with stock air box. I have since posted an ad for air box in parts wanted section and am waiting for it to show up!
I had a similar experience. When I bought my '74 CB750 the PO had already put pods on it. I spent the better part of 6 weeks screwing with them to get rid of flat spots etc. I even bought and installed another set of expensive pods. Thought I had it working not too bad, but I still thought it could be better. Fortunately, the PO had included the stock air box in the sale, so I bought some new OEM rubber boots that join the carbs to the air box and installed the air box with the original stock jets.
NIGHT AND DAY DIFFERENCE!! Now I finally had the legendary CB750 working like it is supposed to!
When I installed the OEM rubber thingme's I noticed that they looked like mini velocity stacks, and subsequently I read where that is exactly what they are and why they are needed.
Pretty hard to do better than the 1,000 Honda engineers that designed the bike in the first place!