Originally Posted by
foama
Often its the small stuff that gets overseen and gives you a hard time.
If you want to check if a valve isn't closed, you could pull out the injector and stick a litte USB endoscope down the injector hole.
On the other hand, if a valve is not closed, compression is gone. If it starts OK and suddenly don't run right, it doesn't look like an open valve.
It could be something simple, like a corroded plug/socket in a cable assembly inside, on the left side and below the dash. The wires from the ECU go from there via another plug/socket to the injectors.