I love knowing things about opiates, and learning things about them too. However I am done with the full agonists, buprenorphine is the only one I want to use again, and only because it helps tremendously with ADHD as well as maintaining a healthy mindset of no full agonist cravings. %)
Full agonist opiates, specifically and especially methadone, will lower one's endogenous testosterone level; this is why I heavily prefer buprenorphine.