I know exactly what you mean with going back and fourth with the subs. And when I do shit as well, I do opiates to the fucking extreme and had a huge HydromorphContin Habit the fourth time I relapsed before being able to find a Sub doctor again. I am on 16mg/day of Suboxone and it barely even holds me. I was almost considering Methadone, but I don't really want to go down that road. But I am hoping for something like Suboxone to be able to save my life, so I can go back to school, get a part time job and start making some real money again for fuck sake. I always feel like I need more Suboxone too. The Subs are not holding me as well as they did in 2009, thats DAMN for sure.. Buprenorphine is a really weird, kind of fucked up opioid in a way. I mean, its good shit, but its also bad shit in another way. On Methadone though, I was never able to get high on other opiates because my Methadone dose was WAY WAY too high.. (190mg's/day of Methadone for 2 years). A 600mg/day Oxycodone habit, plus a Lyrica/Benzodiazepine habit on top of that.
So I know how you feel bro, except I don't IV, and never have. I always just use Intranasal mainly, or sublingual for Suboxone, oral for Oxycodone, and occasionally IM use of maybe hydromorphone. But never have IV'd. I hear SC Hydromorphone is supposed to be close to the B/A of IV. But not entirely sure on that one.
Anyways I was insufflating enourmous doses of Hydromorphone per day, easily over 100mg/day. For years, as well as severe Oxycodone in the past, and the MMT I was on in the past.
My tolerance is sky fucking high, and I hate it. Pregabalin also potentiates benzo's and opiates quite well, so that could add to the B/A as well I'm sure if you timed the dosing right. I was also potentiating with Diphenhydramine on top of Lyrica. As I have been prescribed Lyrica for years, but my Sub doctor wants me off Lyrica, so he keeps lowering my dosage. I told him I need Lyrica during my Benzo taper and I'm having enough problems with the Suboxone already.
I tell you as you already know, its hell on earth once you fuck with serious opioids like fentanyl, hydromorphone, methadone, and subs.
I wish you well my friend.
BTW - I love your nickname. Firebirds are my favourite car, always have been, always will be. Even though they stopped making them in 2002. (THAT SUCKS - They bring back the Camaro, but not the Firebird.)