powder is just as shady as pills, it could be some random RC with an entirely different dosage regime that your shady dealer passes off as MDMA just like his big bag of pipes. If it is MDMA then the experience will be reliability the same if its powder or a clean pill. Many pills have large amounts of caffeine or various nasty's that really fuck you up. Get a test kit, don't dont be rushed, know your source, hell friends who just don't know better have inadvertently tried or successfully ripped me off.
Test everything.... Trust no one. If you get ripped off and cant work it out just spread the word to your friends, pillreports, etc. its the best thing we can do to stomp out the crap pill besides a massive regulatory change.