Clearly this is a common issue (though I hadn't come across it before) since the local Vauxhall dealer had the part on the shelf.

The problem is the "Downstream" ducting on the right hand of the engine bay (looking in) between the intercooler and the inlet manifold.

The pipe splits leaking air, generating a fault code (incorrectly Implicating the MAF) and putting the vehicle into limp mode.

The replacement comes not only as the rubber tubing but also with the hard plastic end bit that connects with the intercooler.

Do not attempt to replace this!

Just cut through the clamp connecting the old rubber pipe to the hard plastic bit with a dermil (Or whatever), remove the old rubber pipe.

Remove the new rubber pipe from the new manifold in a similar fashion.

Fit the new pipe to the old plastic bit and clamp with a suitable jubilee clip.

Doing it this way, literally, takes only a few minutes! (Really I do mean >120 seconds, you do not even need to remove the under shield)

I previously tried to do it "Vauxhalls way" and not only did I lose a fair amount of time, I also lost several square inches of skin from the back of both hands which I am still waiting for it to grow back!