If they are as easy to install as everybody says, then they are also just as easy to remove... Borrow a set from a 'generous' Crossfire owner in the dead of night. Install them on your car in such a manner that they are EXTREMELY difficult to remove!!!
Or, a second option would be to have somebody 'accidentally' rear end you, then when it's ion the body shop tell them the diffusers broke and fell off in the accident.