What Sprout says is correct in chemistry in terms, in practical terms you've probably never been sold anything other than racemic MDMA, since all synth's I'm aware of yield racemic. And racemic is said to be the best effect according to Shugglin, they're not going to do an expensive separation of isomers. That is not the problem.
This was all answered pages ago now. The problem is the precursor switched to PMK glycidate, and the purity is rarely what it should be. ie the MDMA is probably cooked very badly without much care for anything other than profit. Look at what the Dutch are doing with speed, and this "paste" phenominon. Go and have a look for some test results. Dutch criminals who produce these drugs are not very nice people.
The Canadian stuff I've decided is not any better and I think a few of you are trying to convince yourself otherwise. That's why SR got a better whack off it than his mates who weren't absorbed in "this should be better" school of thought. Test results on the avengers are worse for the Canadian than anything else purity wise, some of its still being sold wet even. But what is there is better synth MDMA (made with safrole not PMK glycidate) you just would need to dose more than usual. That said all the Canadians are saying they buy the European stuff because it's stronger.
It's just like everything else, it's all about your source. To actually get good coke, high purity and clean not every seller has it, or even many sellers at all.
Tec's post about says it. Cheap shitty precursor, bad purity. That is it.