Pulled the large fan, as it's motor had gone crunchy.
I thought I'd be installing a fan salvaged from a Volvo, but it turned out to have a slightly larger diameter motor can, which wouldn't fit in the VW motor support.
$50 later, I had a new radiator fan assembly from a car being parted in the local area.
Replaced the crank position sensor, MAF, and air filter, all chasing an erratic stumble/die issue that only showed up at idle, with the engine warm. No fault codes other than a pending code for the CPS. The MAF was tracking ~200mg/str below the calculated value, and was 4.5 years old, so it was replaced as a "maybe" culprit, but the new one still tracks ~100mg/str below the expected number.
I'm still not sure it's fixed, as the issue doesn't seem to crop up until I've driven for ~1 hour before it will happen.
Such fun...