So it turns out the paint did peel off the chin spoiler because I didn't prep, sand or prime the spoiler before I painted it! Shortcuts done in haste never work! So today I removed it and sanded it with fine sandpaper and scuffed it up enough so I could prime it properly with gray primer designed to bond to plastic. Several coats of gray primer which dried quickly. Then several coats of Tungsten Gray Metallic from Automotive touch up. It was easy to see the paint was bonding to the plastic. Finally about four coats of clear. The paint is hard as nails now and looks great and should last the life of the car. I don't think I'll be taking this off again anytime soon.
So when you get your chin spoiler spend the few extra minutes to do it right and sand it then prime it then paint it then cover it all in clear coat. It only takes an extra hour or so to do it right.
"Next time you pass a cop in an unmarked vehicle you better know the speed limit...especially in this car...it stands out!"