for me the secret to picking fast is to pick light, personally I use thick picks and tight string and expose as little pick as possible
when my technique was rubbish I'd pick hard when playing slow and pick light when fast, now I pick light when playing slow and fast, picking hard with distortion doesn't make much difference to the sound since there is compression caused by the distortion (I think)
I also anchor myself with the pinky and mute the strings above with my palm, I used to practice scales a lot and do exercises 1 and 2 and variations of them from michael angelo's speed kills
anyway practice makes perfect, keep going and you'll be hitting 16th notes at 200bpm in no time