First, I agree somewhat with bambambigalo. When I fought there were certain codes of honor, these seem to have been lost. I boxed at a very high level, and PEDs were not really an issue for us at the time because, first, the science behind incorportating them for fighters was BADLY lacking (and when I read threads on boards like this, not much has changed in that regard) and second, most trainers would not want you carrying excess bulk into the ring. The reasons for this are obvious, and both probably apply to you D-MAN...obviously, you need to make weight, so your choices of drugs would automatically be limited to mostly low\non-androgenic compounds, with possibly small doses of fast acting test (suspension most likely, and even then at a low dose and only about a week before the fight, 2 at most) being an option. Second, the greater your muscle mass, the more oxygen you will need to fuel the muscles, therefore your cardio and especially your ability to generate and maintain ANAEROBIC energy (not just aerobic) must be greater. Why do you think guys who would test positive lots like Shamrock late in his career gassed so easy? This is also why people who recommend drugs like Halo or Tren are asking for trouble; both of these drugs have potential to increase your blood pressure signifigantly...try 15 minutes of hard grappling with elevated BP--not too smart.
I do still feel that to some extent this violates the "fighters code" whatever the fuck that means anymore. But having said that, MichaelJThomas is also correct. And if your event isn't drug tested, you aren't violating anything...I am just old school and remember seeing guys take shit to numb pain prefight, or worse, hearing of trainers (in the news, not at anything I fought at) doctoring gloves or whatever. In spirit I agree with regulator the most.
But if you are going to take shit, do more research bro...you haven't even thoroughly researched the effects of b-12 (not taking a shot at you).
Unfortunately though, ultimately times have changed. Look into EPO, Oxandrolone, and possibly some other compounds that are similar. Stay away from the shit I mentioned with the more adverse side effects. And bro, I mean this in the best way, educate yourself better. When you get into the ring\cage whatever, all the "experts" won't be able to do shit when your head is turning purple from high BP or you are gassed from excess weight, or your once explosive fast striking looks like, well, a juice monkey chasing an elite fighter.
Peace