I've been playing guitar for almost 6 years now. I'm pretty good and all, but I haven't improved much in a while.

I was wondering if anyone knew some good ways to better your technique once you plateaued. I guess my sweeps need to be improved. Fast riffs (Decapitated Sphere of Madness-ish) could be a bit more cleaner. Maybe some soloing as well. Also learn scales besides the pentatonic.

Any ideas where to start again?
you pretty much answered your own question. other than that get a metronome, try some different tunings, and practice, practice, practice!