Can't say for sure, different for everyone... During the detox process (even on subutex) all sorts of things are going on within. Neurotransmitters trying to figure out how to connect on their own maybe..? Don't know for sure - but I do know, and from more that one experience, you will go through some emotional issues. Some good - some not so good. Happy, sad, etc... and anger IS and emotion. These things will happen, and they diminish in time.
Oh, and the good stuff seems to kinda take over in time. Yep.. I know. Tough to deal with for now.
Hang tough. You'll be OK. Really.
Week 3 'OFF' of Subutex after years and years of
MS Contin, Methodone, etc. and gettin' better, gradually.