Hey Drazh, your post is rather vague but I might have some info that could help. Most tension issues arise in the wrist.
I was watching an interview with Ivo Pogorelich's teacher. She said that even when playing fast sections or octaves, etc, there should always be a wrinkle on the back of the player's wrist.
For those of us with skinny wrists (like me) there is no wrinkle, but the point is, your wrist should be loose and flexible, not rigid. If you have a teacher, ask him/her to push or slap your wrist while you are playing a fast section, to check the tension.
Of course there are a lot of subtleties here and a lot more can be said. Maybe this helped a little though