If you dont use the stock airbox, the bike will never run right. You need that restriction on there, something about the flow pattern goes off when you run pods. I did the same thing to mine and the bike always ran lean no matter what i did. Free flow intake will not work on these bikes. Also, you need to get a vacuum synchronizer. It's the only way to get them spot on. If you look at the intake runners, you will see the ports for the vacuum syncrhonizer. They are capped off. get the caps off and buy some adapters. run the bike up to 3500 RPM and adjust til all the carbs are pulling the same amount of vacuum.
I met an old Japanese bike mechanic at my local Honda dealer who taught me more about this bike that i ever wanted to know. If you have anyquestions, let me know.
Get the stock airbox on there. You may be surprised at how well the bike runs. One more thing, periodically remove the valve adjustment caps and clean the threads/ put some anti-sieze on them. I used to break these stupid things all the time.
Try these guys for used jap bike parts. They have a HUGE boneyard full of these bikes.
http://www.tricountymotorcycles.com/ I guarantee you they will have whatever you are looking for.