Well, addictions docs and the makers of Suboxone are quite adamant that the naloxone in Suboxone will essentially deter IV abuse. The truth is that buprenorphine binds to opioid receptors so strongly that the naloxone won't exhibit any antagonist activity, even in very large doses. This essentially means that the naloxone won't kill a buprenorphine buzz. Throw in the fact that buprenorphine is quite strong in terms of mg potency, and that's a possible explanation as to why you're getting high off of subs.
Just be really careful messing with buprenorphine as in overdose, it's quite dangerous. Yes, it does have a ceiling effect on respiratory depression, but treating a bupe OD essentially consists of putting the patient on a ventilator and getting them up to ICU to let the bupe clear their system. Even very large amounts of injected Narcan frequently do little to reverse a bupe OD. Also, make sure that you're not combining the IV bupe with any other CNS depressant, as that's when bupe starts to get really risky.