rgwm on here may have some pieces of 155 lying around... but it's the joy of a non-code car that you have one less thing to worry about!
ECU failure is a bit rare though so I'd really look for something else in the meantime.
I presume you checked the fuel flow by whipping the rubber feed pipe from the fuel rail before the pressure stabilisor doodah?
Do it again to convince me..
Plonk the tube into a container and crank the engine over. Does fuel come out of the rubber pipe ?
If so... make sure it's getting to the sharp end. Test 2 is to remove the return pipe (catch the fuel that comes out). It's the rubber tube at the fuel rail, on the left... next to the chrome pipes that disappears back to where the inlet pipe came from).
If no fuel comes out of the return pipe, then there's a pressure regulator problem potentially. (When you're asking around for ECUs also ask for a pressure regulator).
If fuel is arriving into the rails then Test 3 is to make sure it's being squirted. You can remove an injector but let's assume that most of them didn't suddenly stop working. Check they are being "fired".
If you don't have a multimeter.. use one of those glass bottom ("number plate") bulbs.. Bend the tangs and "insert" them into the teeth of one of the injector connectors. When you crank the engine, the meter/bulb should "pulse". If not, then the injectors aren't firing so that would stop the beast starting.
If there's fuel and your injectors are injecting it, then check that the plugs are kicking it all off. Do you get a spark at the plugs? Do the sparkplug-earthed-on-the-motor test. Does the HT deliver a spark to the plug?
If you have sparks and fuel then it must fire...
but my guess is that one of these ingredients is missing.
Don't worry checking every injector or every plug.. if one works then they will all work. Your problems sounds a "global" one rather than peculiar to one cylinder. My old beast has started on 4 cylinders before..