I can't help you with the NIBBI, as I have never owned one. My go to carburetor for PWK and PE when I am going to spend the money is a genuine OKO carburetor built in Taiwan. It is a copy again of the Japanese designs but must be good because the Chinese copied a copy with the OKO logo cast in and pass it off as the real deal.
I suspect it is popular in the Asian countries.
A genuine OKO you can only get in certain places and many times there is a national distributor too. They are not a flashy piece of machined aluminum they just get the job done. I own several and I like um. Don't mean to monopolize your carburetor threads, I just have strong opinions.
http://oko-australia.com.au/