The cam follower runs the high-pressure fuel pump thats at the end of the fuel rail bolted to the head. There is a 'design flaw' that causes this part to wear out and then it'll mess up the intake camshaft and the fuel pump.
The cam follower is a $50ish part that you can relatively easily replace and keep more expensive/time consuming repairs from being necessary. If you have the banjo bolt fitting on the fuel pump, it's a little tougher, but you'll get the hang of it. I traded my GLI and still have all brand new parts to update to the later style fuel rail without the banjo bolt if you're interested.
And to answer your original question, an upgraded HPFP while you're in replacing the follower, accompanied with the appropriate tune, will get you a little more umph.