What I've noticed lately while working on my speed chops is that in order to pull off a fast passage and to make it sound fast, you need to play with very even volume and make each note "sound", so it doesn't blur out.

A cool way of getting something to sound "fast" is to mix two diffrent tones, to gain contrast which will enhance..like two muted notes followed by one or two played one....like:

G----------------------------------
D------------------x-x-1-1-x-x-1-1-x-x-3-3-x-x-
A--x-x-3-3-x-x-3-3------------------
E---------------------------------
and so fourth...
if you play the muted notes with even volume as the played notes it will somehow trick the ear :P
(All notes are 16ths)

Ok I just felt like sharing this ;)

/lovebown