yeah, ive had/been sold some molly last year that whatever it was wasnt MDMA, wasnt pipes (or at least ive taken piperazines/been pipe'd before, wasnt that), wasnt amphetamines (or at least i didnt get spun on it, i LIKE amphet a lot so i would know what it feels like...), and whatever it was didnt dime my pupils yet provided a strange mild high.
There IS fake molly about, id be willing to bet that as long as it tests up good the only cuts are gonna be inactives or maybe caffeine. I dont think people bother putting speed in molly, but i have heard of pipe mix molly if i remember right with just a teensy bit of MDMA to fool a tester.
Id be more suspicious of worrying about that if you get sold straight up white powder. I've had good white powder MDMA before (its relatively common) but id feel a lot safer buying either crystals or brownish shit, but thats just me, i wouldnt buy "molly caps" to begin with.