BEPUphysics

does appyimpulse wake up the entity because im experiencing sleepy grenade problems

Unfortunately, no; it doesn't wake objects up. This is a known problem and will be fixed with v0.3.0 (or an earlier patch release if it becomes apparent that 0.3.0 is going to take too long). Until then, using (Entity).isActive = true immediately before/after the applyImpulse call will force the object awake.