In my quest to discover more working horses, I'm wondering if this is normal, seems to have gone unanswered 'over there'.

Most times when I stop the engine, I get a strange sound that seems like something is being released, but it isn't the EAS. Sometimes it can be heard as a sort of ongoing noise while the engine is running after starting. It is loud enough you can hear it inside the car. It does seem to be coming from right side of the bay (when looking at the engine).

So, does your GEMS make any odd noises at all when you turn it off?

Could be the evaporative thingy that lurks on that side with the pipe connected to the inlet manifold. Very, very occasionally, and it hasn't done it for over a year now, mine would start and idle fine but do nothing when I pressed on the throttle. This was accompanied by a sort of moaning sound. If I switched off and restarted it would fire up fine and the noise would be gone. I has assumed that was coming from the EVAPs bits.

Yeah, I'd be looking for vacuum leaks around the evap plumbing and possibly cruise control valves. The pipes to the latter split and suck air in.

Right. I'll try and record it sometime, just in case I'm making a hash of describing it, but it sounds a bit naff. I can't say I've heard it on any other petrol engined car I've had - they just come to a nice quiet stop. The old engine did it as does the replacement, so I figured it was normal, I didn't consider the evap stuff. I can't remember if the old one would pop on the overrun, but it had the exact same slight unevenness in the idle despite leads, plugs, sacrifices, and now another engine.

I'll have to do some investigating, may build a smoke tester. Do you know if you can disconnect the purge valve electrically, and block the port on plenum for a short time without really upsetting something? After testing the purge valve isn't leaking through venting vapour into the bay while disconnected of course.

If this P38 my parents have acquired was a GEMS I'd be sorted for comparisons and bits to borrow. Sadly it's a Bosch/Thor, and it runs sodding lovely doesn't it.