There is a simple comp test you could do whilst waiting for the gadget to turn up.
Spray some WD40 into the cylinders on the LHS, put the spark plugs back in, crank the engine on the starter motor. Look down the inlet tracts through the throttle bodies and if you get wisps of WD40 coming back up the inlet, then you have no compression. This will tell you about the 4 inlet valves and whether they are closing. Clearly some of the WD40 will go down the exhaust, which would be much more difficult to determine, but it would all go that way anyway with no combustion.
One thing I always did when I was having the over fuelling problem was when I was taking the plugs out, (you get pretty quick with the right Alfa supplied tool) is to clean them up properly with one of those kitchen blow torches used for melting the creme brûlée (posh….. I know). It made a huge difference when re-cranking. I could take four plugs from an engine that would not catch AT ALL, clean the plugs up in this manner and it would fire up almost straight away. It would then run for about 20 seconds, the idle would slowly die away and the engine would not then start. In trying to find the problem on mine, it would short circuit that 2 hour wait that you mention, down to 5-10mins to clean the plugs up. I must have done it a dozen times, letting it run for 20/30 seconds, trying to gently increase the revs so it would catch and clean out the bores / cylinders. Every once in a while it would - but most times, as soon as you ever so gently squeezed on the throttle it would just die. Once or twice it caught and I could get it up to normal running, thinking I had restored it, but next time I came to use the engine it would start, idle then die.
When cleaning the plugs with the little blow torch, I did get the plug quite hot, to the point where the metal was about to glow and the ceramic turned whiteish again.
Another suggestion, is if you start to drop the engine and you do lower it on one side, when you have the cam (metal) covers off is check the operation of the cams and hydraulic tappets before you take the heads off. I am certain that this might tell you something. Clearly if the cam lobes are turning and the top of the tappets are moving exactly all in sync then it is not that - but worth doing that before you finally whip the head off.
Some other thoughts - swap the ECU for a different one?
Butterflys, actuator arms all opening simultaneously and correctly and positioned for idle?
Earth strap firmly bolted in place. You can have spark - but is it a good spark? Strong, strong battery. I let mine run down a bit after loads of pointless, frustrating cranking, charged it up - fired up straight away.
I also hate 33's at times. Stop, put the kettle on and find something else to do - go back with a fresh mind and come at it from a different direction…..
It sometimes works…...