Either goo be gone or lightly and I mean Lightly wet sand with 1500 Grit paper, then buff out with some sort of compound, like meguires ultimate compound. You kept the grill badge right??? JKJK
Edit
Goo Be Gone
Meguires UC after light wet sand
Goldie 98 Topaz Gold GTP (retired)/ Shadow 06 GTO 6.0 Phantom Black Metallic- traded in. Now cruising a 2005 GMC Sierra 2500 HD 4x4 with the always fun 6.0L