Have you considered or ever heard of the 24 combination approach? Example. You can play 24 different combinations of "1234". I will only list from the index finger here.. 1234, 1243, 1324, 1342, 1423, 1423

You can do this starting from each finger. It is a good exercise to help separate out the mind from the hands. I believe that guitar is 80 percent mental ability and 20 percent physical.

These exercises can help with speed but like anything else I think the real answer to speed is to practice alot. Stevei Vai once stated in one of his training videos that he got himself to the point where he would practice one riff or line for one full hour.

He started out at 5 minutes, then 10 the next day, and so on until he was up to 1 hour. You need to get intimate with whatever you are trying to play, especially if you are looking for speed.

I personally try practicing my picking with a quarter also because it forces me to hold my picking hand so the quarter is "flat" against the strings, as it should be. Guitar players tend to lean the pick on an angle, but if you want speed you gotta be perpendicular at all times between pick and strings.

Good luck

:)