'"High" tolerance to H could mean almost anything; you could have legit diamorphine hcl of high potency, or stomped on powder from the NFC North, or Base, not to netuon tar...
Don't really know of much value in this, at least in the way you posted the question: will not encourage a needle, will not pretend it will be amazing if your slamming southeast powder, going through grand if you take it by mouth
Assuming it is MS Contin or equivalent, 1 or two would be a starting point, wait at least 40 minutes to redose, and crush the tablets if you want to break time release; it has to be taken by mouth or injected, and again, can't recommend injecting, certain formulations aren't really suited for it anyway, as they gel
take it slow at first, and it should work out; morphine is a powerful drug, and aside from the onset, the effects are pretty much the same as H at the correct dose(H itself has no practical effect, it is rapidly converted into morphine, just a faster onset, for the sake of simplicity
Unless you have something to add that is all from me