D.K.
It is totally time to seperate them at naptime, period. They will continue to feed off of each other and egg each other on.
Be firm in your tone, lay them down and tell them it is nap time, put one in one room in a pack and play and the other in his crib if you have to, make sure the room is keeping out the sunlight. During the day they can see each other and feed off each other and it will get worse when they discover more cool things like jumping, climbing out and so forth! Good luck.