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A desnorkled airfilter only runs properly with uprated jets and a race can. It's essentially just a race filter when you cut all the top away and you can clean it then with a toothbrush.
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All together now: Oh No It's Not!
The biggest difference between the standard filter, the BMC Race filter and the BMC Race RS filter is the material it is made of and, as a result, how much air it can flow.
I did some testing at the start of last year. I desnorkeled a standard filter and tried it back to back with my MHP race system. Despite trying everything from 137.5 to 165s (Mikuni sizes, not Dynojet) we could not get it working properly.
Later in the year I did a similar test with two BMC filters. The Race is effectively a desnorkeled filter but with freer flowing material. It worked okay but the Race RS (the on with the big hole in the top as standard) was really good. We tried to work out the difference between the two and cut a similar hole in the top of the Race filter.
Strangely enough the Race filter, despite having exactly the same hole in the top as the Race RS didn't run the same. It's all down to how much air the material element can flow. The standard filter just can't flow enough air and desnorkeling it makes a mess of the air flow.
I spent several days last year trying different things on a dyno with different filters, jetting and needle positions. I can vouch for the results with a BMC Race RS filter and a Dynojet kit. I have also seen good results with the Renegade kit although I didn't test it on my bike.
As I said in my earlier post I have not found anyone inthe UK who has managed to make a desnorkeled standard filter work successfully on any bike that has an exhaust that can flow better than standard!