The gasket set and timing set came in last night. The timing set looks good ... haven't scoped out the gasket set, yet.

So... a quick update

I removed the air compressor a couple of days ago and took it to someone competent in the art of refurbishing air compressors. He didn't take long to figure out that the compressor wasn't pressurizing as quickly as it should and that the internals needed overhauling

I ended up buying a refurbished compressor from him, but a quick post-installation test unearthed a couple of issues: the temperature reading was out of whack, indicating a bad sensor which both he and I confirmed by comparing resistances against a couple of other temperature sensors.

The second issue is what I'm stuck on right now. The compressor pressurizes the system OK but can't vent air when required because the exhaust valve doesn't want to open up

As it stands, the rear air springs are jacked up way above the height they should be at. Bugger

@Zaid - If it isn't one thing, it's another! Getting closer, my friend!