You can sometimes make a poor Generation (though not a stiff- necked one) better if it has a lot of moulding flash in and around the fipple- remove it very carefully with a very sharp craft knife. Be careful not to remove too much, just any obvious stray plastic. But keep practicing breath control and make sure you are covering the holes securely. Most whistles are pretty dodgy at the top end anyway, but I've played Generations for, well, generations now, and I find them as good (when good) as almost anything else. The quality control does seem to have improved somewhat in the last few years.