OK... I'm 3 rums in, hopefully I don't sound like too much of a cock, BUT...
Just start at the beginning of this thread and actually check the bare basics as suggested. So far, there's been a whole of of time wasting and money spent with incompetent "mechanics" and the bare minimum checks haven't been done!
These V8's are NOT complicated and the garages who looked at it are clearly morons. Forget EVERYTHING they have said, forget everything you think might have happened and everything that could have happened and start with the basics again.
Apply logic, record the results and THEN determine possible causes. This whole thread and process has been so all over the place, with zero logic and process.
1: Compression, is there any?
2: Spark, is there any? Is it at the right time?
3: Fuel, is it beng injected, does ezi-start make it fire, pop, fart or explode?
It needs air and fuel into the cylinder, it needs to compress it and ignite it.
Which part isn't working? It was probably only one of them at the start, since it just didn't start one day... but by now, there could be multple faults, introduced by dicking with things without doing the basic tests. Those garages sound like the exact places that should be avoided at all costs.
Also, If you want to own a 14CUX injected V8 for any period of time, GET ROVERGAUGE - you can build or buy the cable, and the software is freeeeeeeeeee! I can run it on my phone (RS-RV8) or laptop. You can see what the ECU sees, instead of guessing. But's it's still only useful after the basics are determined to be functional!