The Mark 5 Golf GTI with the FSI Turbo engine has a weak point; the High Pressure Fuel Pump cam follower. They like eating themselves and taking the cam with them.
Step one is to remove the cover with stupid integrated air filter
High Pressure Fuel Pump (HPFP)
Easy to remove, just don’t be like me and break the farking clip off the sensor plug. Zipties to the rescue. I’ll get a new plug and repin it at some point.
Leaks a bit of fuel and oil when removed, but otherwise straightforward. I did not remove the rubber hose under the pump, I left it connected.
Pulled the follower out and HAPPY DAYS, it’s in good condition with moderate wear. About what I would expect if it had been replaced 30,000km or so, so someone has done it in the past. Cam lobe looked good.
Popped all that back together, primed the pump to check for leaks, all good.
It’s great knowing it’s been done, and that it won’t chew into the cam and cause all kinds of hurt. Cheap insurance really.