Generally, molly can be detected in a urine test up to 3-5 days after taking it. It can be detected in the blood 24hrs to 2 days later and it can still be detected in a saliva test one to five days.
Like many other drugs, it is detectable in hair follicles up to 90 days after ingestion. But there are still a lot of other variables that determine how long Molly will stay in your system. Things like your age, body mass, hydration level and overall health will influence it.
Molly is the name given to a purer form of MDMA than ecstasy that comes in powder or crystal form as opposed to a pill. It is said to be cleaner than ecstasy and is widely available in city centers around the world.
The thing about molly though, as with all illegal drugs, you never know exactly what is in the mixture that you are taking because you don't know who or where it was produced.
These drugs are produced in the black market, and there are no regulations and guidelines overseeing their production so you could be getting something different each time.