Trying a simply X-Factor trick with Doom:
Air Plasma Beam => Air Photon Array => X-Factor => Air Plasma Beam => Air Photon Array
Simple, right? Well, it doesn't work. After the X-Factor, you can either do a Plasma Beam or a Photon Array, but not both. What I don't understand is why it doesn't work. You can do it before the X-Factor, so why not after?