am i completely wastin my cash
Hate to bare the bad news, but I think yes....
Asking your question in The
Other Drugs section of this site will yield a lot more/accurate answers.
I'm pretty sure black tar herion is fairly rare in Australia, I'm sure it's there, but from you mentioning it, that made me think your from America. Ask some folks in an American forum for better advice regarding black tar.
Your dose of methadone, and how long you've been taking it for, would be helpful information for people trying to answer your questions
One thing I have heard is, if your on a high dose methadone for a prolonged time, your general opiate tolerance could be redicoulous, you might find that the black tar does nothing to you, and hence become a pointless task (and slightly risky).
Don't quote me on this, but if you go days without methadone so you can get high on H (lowering your tolerance so it works), you could quite easily overstep your H dose and ultimately overdose.
EDIT: after a slack research I've found that you will need redicoulus amounts of H or any other recreational opiate to feel anything you desire (a costly cause), nothing I'm advocating at all, this is a harm reduction site so I'm slightly against what your trying to find out.
I have no experience in this field, but these are what I've found so far.
Research friend, there's heaps of people out there in your position.