i can only speak for myself - no guarantee that it will work for others too - however..

i once was in some kind of rut too. the thing that helped me out was classical. i started to work on the most difficult pieces i could find. i came arcoss some realy wierd stuff and unusuall scales, strechings, chordfingerings, etc. It was extremely challengeing and helped me within only a few months do make a quantum leap in both shred and precision. for once you can play sh*t like Fank Martin or William Walton, a simple fast scale run will be like kindergarden for you.