I‘m actually not active in this forum … I just wanted to browse a little in it and the first thread at the top (this one) caught my eye.
I suggest the following:
1.) Check if the air flow meter plate moves (about a centimeter or so) away from it‘s (correct) rest position when you (try to) start the engine, and check if it moves further down if the throttle is completely opened during starting.
2.) If that‘s the case, check the fuel pressure … “system pressure“ (SP) and “lower chamber pressure“ (LCP).
... I start to have the feeling that there might be not enough fuel pressure to make it all the way thru the FD to the injectors. ...
Assuming that there were no issues before you replaced the FD filter fitting, there might be too much
fuel pressure … in the lower chambers that is. … With ignition off
and fuel pumps running, LCP shoud be at least 0.3 bar (4.5 psi) lower than SP.
If the difference is smaler … and I‘ll have enough time
… I‘ll explain a possibly helpful next step.
If that step will be successful, I‘ll tell you what happend when you replaced the FD filter fitting. …