Ack! Bring back the Trashyk! (Seriously those things are worth almost two imps in the damage they do) Or at the very least the old new fireballs...
EDIT: I should also note that the minimum distance between two imps needed for them not to be stuck together is 32, so giving all your imps a radius of 16 (incidentally the radius of the player) and using A_SpawnItemEx is enough to solve the Map01 UV problem.