@Pudding is right and this is what VW will recommend too.
BUT
This issue arrises from filling the fuel tank to the max, the activated carbon cannisters job is to filter harmful gasses from the fuel tank but by brimming it, fuel can often travel into the PAC and saturate it which will throw up the fault once more. (This is all based on what VW have told me and general consensus on the forum).
When VW insisted I replace mine, I demanded a warranty that this issue wouldn't arise as soon as I brim the tank again but they were unable to offer it.
Moral of the story is, if you replace it, it can come back so why bother? I cleared the fault with VCDS and it hasn't come back in 2 years after the first 4 or 5 clears.
Separately, those rubber bumps I guarantee were at the back of the cover (toward the windscreen). More heat generates here and the rubber naturally splits, it happens to everyone and you can replace them for about £1 each. I think the part number is in my build thread -
http://www.mk5golfgti.co.uk/forum/index.php/topic,89715.msg907250.html#msg907250