Evolutionary Leap Stack Ordering
Pulmonic Sliver's ability is a replacement effect and doesn't use the stack. That means that when you pay the activation cost for Evolutionary Leap, you may choose to put Pulmonic Sliver on top of your library, and as soon as Evolutionary Leap's ability resolves, it will find that Sliver. Most of the times, that is not what you want, but fortunately Pulmonic Sliver's ability is optional.