In order to be able to play real fast you need a lot of practicing. There's a certain barrier that you surpass without being aware of it and, from that point on, nothing can slow you down.
Almost anything can be played fast if you practice correctly: begin slowly, then increase the speed gradually.
But there is also another little secret: the efficiency of your moves. Press the strings with your left hand with the minimum power that gets the right sound. You can even practice this technique. Let's take two simple chromatic runs:
Play these two runs without pressing with your left hand's fingers (a kind of "left hand mute") until you are able to play them fast enough. Then increase the pressure until you reach a clean sound but don't press more than that. The purpose is to be aware of the minimal pressure that's needed.
Now, for the right hand: play tremolo picking on a certain note. Play at all the intensity spectrum: from soft to loud. Be aware of the right hand move. Make it as efficient as you can. Play tremolo picking on all the strings, the angle of the pick is very important.
You need only 5 minutes a day to practice these exercises and you may give them up when your moves will become real efficient.