When listening to some of the great pianists of all time like Horowitz and Rachmaninoff, sometimes the fast finger passages sound almost jewel-like in the shimmering clarity of the notes. One of the secrets to developing this kind of technique is practicing slowly with raised fingers. You see, it is not just the placement of the attacks of the notes that creates this pristine evenness, it is the precise release of notes that gives the even spacing that creates the trademark sound that is so beautiful.
Try putting your fingers on a table and lifting each finger separately. You will notice how difficult it is lifting up individual fingers, particularly the 4th finger. By practicing slowly with raised fingers, you will develop the strength of the release of notes which will enable you to get that glistening stream of even notes in your fast passage work that is so compelling.