I use the BOSS Metal Zone MT-2. The different settings for the knobs on the manual shows different distortion sound suggestions, but when switch it to the setting, it sound nothing like it. In fact, there's no distortion at all.
Make sure the cables are set right first, and after that just go by ear. Choose what sounds good to you. If you keep having problems contact BOSS and they will help you, they were a great help to me.