Purity - MDMA and complaints...

[pinkandfluffy]

Okay, so recently my pet has doing "pure" MDMA powder with his friends. He has picked up a half O twice, and is pretty sure theres only one or two links in the chain before the actual chemist.
The first batch was pretty fucking good, and everyone loved it. However, the second batch (of which he's still got about 4 grams) seems to be picking up more complaints. There seem to be people complaining about throwing up because of it, and not on the come-up - actually a few hours after feeling effects.
The other complaint he recieved is about potency. Four friends snorted 500 mg (making 1/8 of a g each) and felt nothing. He told them that they didn't take enough, and the standard dose he tells people to take is 250 mg. Does quality of MDMA vary that much through the skipping of impurity processes? I've been lurking here for a while (this is my frist post!), and see people talking about 100mg being enough. The other obvious option is that its been cut: He asked for it in rock form, but got it both times in powder, with apologies. Does the vomiting + amount needed sound like this is so? If so, he won't pick up any more.

Also, what would it be cut with? When snorting it when he first picked it up (to test) his nose went a bit sticky, like damp sugar residue. Wouldn't this be a stupid thing to cut it with?

Sorry about the length: TO CUT A LONG STORY SHORT: People have been throwing up more than is common and have needed pretty high doses. Is it cut?