StephenRC45 has an NS400 that I think he was going to fit MC21 carbs to at some point. Maybe you could compare notes later?! He'll be doing some dyno runs on my MC21 shortly, so charts will be available for you all to laugh at soon.
I bought my Ramax filters from a local scrappy who just had them sitting on the shelf. I figured I would bond the foam part to the original rubber rampipes but when I offered them up, by happy accident, they were exactly the same size as the NSR carbs! Cost was about £40 for the pair though, so not exactly cheap!
Andy.
NSR-WORLD.COM