Great information again, thank you. I had the car up on a hoist last night to change the ruptured rear accumulator spheres (apparently DOT4 was once added in place of hydraulic oil) and took a peek at the WUR, (tried) also to eyeball the AAV. In the way of seeing the AAV were the cruise actuator and what’s left of the smog-to-throttle linkage.

The WUR doesn’t look tampered with - encouraging - and the crust of grime blockside of power steering pump suggests nobody’s delved deep for a long while, if at all. So the AAV is probably in a more-or-less original state. I’ve skim read the BenzWorld and Jag Lovers’ threads on AAV dismantling/tweaking, and will be re-visiting them.

Coolant flush number 5 this weekend - have switched to a truck grade product due to amount of fine iron oxides in system - following that will check vacuum lines, and thence timing.