Better adhesive removing solvent?

[bradleyheathhays]

I've been letting some original Goo Gone formula sit on this for a couple nights now and it doesn't seem to be touching it at all. Any suggestions for a better solvent/whatever to get this gunk off before I put the new decal on?

 

[TerryMason]

I've always loved Goof Off, but it's likely the same as Goo Gone.
You may also try warming it up with a heat gun. Maybe carefully scrape it with a plastic scraper.

I think it's one of those things where you stick at it a couple of days and it wears off.