I strongly, strongly recommend against doing this combination! 25i alone has killed a lot of people, even some at normal recreational doses. Add MDMA in there and the chances of a serious adverse reaction are going to be greatly increased. If you value your life and health, I urge you not to take this combo.
If you're gonna do it anyway (which you shouldn't by any means), do it with other people in case something happens, so you're not all alone when you collapse or convulse.