crud

I removed a cracked "Load protector" panel from my CLK and it's left all the double-sided foam tape crud behind.. What's the best way to remove it? (Probably not a razor as the bumper cover is plastic?) (Not sure if the link will work, but let's try it!)...

Well finally bought a new MAF insert today, but in removing the engine cover looks like my Injectors have been leaking a long while (another thing Stuttgart in Ponty failed to spot, so not even sure they changed my oil after my last rant in an earlier post tonight!) Anyway is the black crud...