You put it on but don't know how to take it off? :eh:

It is probably held on by a few bolts. Undo the bolts and it should fall off. Then go to a body shop, have them weld up the holes and paint over them. Drill holes for the ITR spoiler, and bolt it down.

Going from an aluminum spoiler to an ITR spoiler isn't exactly de-ricing your car, but it's a step in the right direction I guess.