On the plus side, I've done this enough times now that it takes about ten minutes.

While fitting this I made a point of trying to get some of the slack out of the throttle cable as there was a lot of dead travel in it before which made applying anything more than about 40% throttle really awkward.
I was then slightly delayed at this point by the battery being flat. I have been doing a lot of stop/start work lately and it was never charged while the car was off the road as I can recall so not massively surprising. Conveniently due to the low power draw of the Invacar's electrical systems, the 12A of charge current from the charger is more than enough to meaningfully help as a jump start (as I recall I measured the current draw of the Dynastart while cranking to be in the region of 30A). While there was initially a lot of spluttering, coughing and one properly shotgun loud backfire while the residual carb cleaner was expelled and a bit of faffing around wishing I had three hands while I got the idle mixture dialled in, we were soon back up and running.
It seems that whatever blockage was in there last time we were successful in dislodging this time.
So, on to the test run. I set the camera running before I started out on the test run. Unfortunately because I'm an idiot I totally forgot to close the offside window so there's a heap of wind noise. Sorry. Equally the camera aim is horrible - again a limit of the holder and that location. I've got a couple of alternatives on the way from Amazon as we speak to try in the future as I'd really like to be able to get *decent* driving footage. This gives a better idea of how she's actually running now though at least. I do note that I appear to need to poke the tail light earthing arrangements again as the indicators stop flashing when the brake lights are on. Think it's time I just rebuilt those lights with better lamp holders and proper wiring as they're nothing but trouble.
(No, I haven't wired the gauge pod up yet either.)
She will still stumble occasionally if you crack the throttle open instantly from idle, but I haven't been able to provoke any sneezing today. If you make a point of smoothly rolling on the throttle rather than just cracking it open, cleaning the carb and having tweaked the idle speed up a bit seems to mostly have resolved that. I do wonder if a throttle damper might be something worth thinking about here.
The low speed/low throttle behaviour has been vastly improved. It's possible to sit at 30mph now without the car complaining which is a nice improvement. It was always a bit hit and miss, but you generally could provoke a sneeze from the carb by hitting the throttle hard after coasting for a bit. I've deliberately tried several times today but wasn't able to replicate it - so am tentatively labelling that as fixed by cleaning the carb more thoroughly.
What it hasn't done anything whatsoever about is the fuel lift problem. The carb still ends up wet with fuel after any period of hard acceleration, and there's still little noticeable difference between 70% and 100% throttle. I'm really not sure what to do about this...If the air cleaner was a better seal against the carb body it would be less of an issue, but as there's a sufficient gap there that any fuel mist that lands on the inner surfaces of the air cleaner housing eventually run down the inside of it and then down the outside of the carb intake, then down over the body. I wonder if it might be possible to fit an O ring to seal the base join between the air cleaner and the carb? Obviously would need to plug the two cutouts (which allow it to close to clamp onto the carb) with something flexible too.
I'm not sure this is something that I can hope to resolve with the carb itself as it (at least if my understanding is correct) is more a function of resonance effects within the inlet manifold itself causing pulses to force fuel back up through the carb when the inlet valves are both closed. Alteration of the air filter side of things to mitigate the effects of the phenomenon seems to be the order of the day. Figuring out a way to properly seal the air filter to the carb *seems* to be the easiest avenue.
It's not a massive problem, the fuel doesn't exactly wind up pouring everywhere, the carb body itself just tends to appear slightly damp to the touch after a run and it evaporates entirely within a minute or two of the engine stopping. I'd obviously prefer *not* to have flammable liquid, no matter in how small quantities, winding up in my engine bay anywhere other than inside my engine though. Long term it's definitely something I want to get rid of - especially given that the road layout around where I live means that full throttle blasts are a necessity pretty much any time I go out whether I like it or not.
On the plus side though it seems that she is running pretty well again. Only gremlin that really came to light was that I do need to put a tiny amount of slack back into the throttle cable. It sometimes hangs up with the throttle held open by about 0.00002%, holding the idle speed up just high enough that I can't engage drive. Simple enough to fix though. Oh, and I need to stick the battery on to charge...Would have done that tonight, but as the Citroen is heading into the garage this morning it needed to spend some time on the charger as it is in need of a new battery and struggles to hold charge for more than a few days.

Once she's got a fresh MOT on I'll get that battery replaced - it's still under warranty so will be getting swapped out as soon as the car is actually mobile again. The car is at the garage having the stuffed suspension bush replaced and a fresh MOT done as we speak.
I made a point of borrowing my husband in the evening to get a bit of exterior footage of the Jag at something other than idle...Sadly I think I really need to re-shoot this with the camera a bit further down the road as it sounds like that's where the good stuff really was based on the distant howl! Makes sense given it really picks up in the mid range.
The theatre of the way the whole car rears back when you give it some throttle from a standing start really hasn't got old yet.
While we were at it, I was curious to see if the van actually sounded as ridiculous from the outside as it seemed based on my hearing it bouncing off buildings and such.
Yep...That's about what I expected...Sound clip that could well be from a good few decades ago!
Both of these need to be tried again with a better vantage point and when the traffic is quieter.