L.P.
i have a daughter and hubby that are extreme cases of add. but you sound more like my friend describing her son who has a more mild case of it.
ADD has common effects on kids/adults such as blurting out w/o thinking first, angry outbursts out of the blue as you describe, unorganized in school thus getting lower grades due to lots of zeroes from not turning in HW (my daughter's IQ is 139-extremely high and w/o help she gets d's and f's), either extreme social skills being vivacious w everyone or the opposite spectrum w no social skills, fidgeting/keeping hands busy or singing/humming while doing something, etc.
My friend took our suggestion to go to our CHILD psychiatrist and CHILD psychologist/ADD COACH who both specialize in child ADD (different than adult add). Her son is now diagnose mild ADD range, and "finding" the medicine helps the best to relieve these.
However, understand that teen time is the time they do blow up, so since you describe that you have been having success w behavoir modification, how much of this is add vs. normal teen year attitude?
Believe me, meds are wonderful but dont get the ones that "make them zombies". but depending on the degree of add, these may not help "enuf". I have found physicians other than CHILD psychiatrists/ADD coaches do not have a great handle on meds and the needs of ADD kids in the best of circumstances.
The other way is knowing to pick your battles during these arguments. Dont get in his face EVERY time...it just worstens things. Dont propogate the argument - instead leave the room&him alone. Once he cools down, talk w him trying to come up with some ways to cope w his anger. Dont accuse, just approach him as if you want to help him fix it.
also, for our 11 yr old daughter, we have found in extreme cases of her acting up that making her sit in one spot for 30 minutes time out w nothing to do is the worst of punishment due to her needing to do "something" at all moments.