[Dr K]

3M General Purpose Adhesive Remove. Make sure you have LOTS of ventilation (perhaps a fan blowing across and another fan blowing out of the garage). Also works for adhesive on rear seats. You can wet a cloth and hold it against it (easier for the engine compartment if the car is on a rotisserie...) for 2-3 minutes, and it will wipe off easier. If you leave it too long, it will take off some of the paint, too (10 minutes did it for me). They generally have this in stock at Strosniders, and I have some you could borrow (and I'm closer than either Strosniders, especially if me meet at NAPA around noon today).

Are you replacing with the Porsche part, or the reflective and lightweight mat from the guy who does the RS door panels, or something else?