Another slightly off wall suggestion.
Have you tried starting with accelerator half depressed?
I had issue with startup and idle, but higher rom was ok.
Turned out to be the ECU wrongly firing injectors it’s twice per cycle, but only at low rpm!!!
I have also had issues with delamination of the flexible fuel lines leading to and from injectors which intermittently caused issues. Not at same time as above
Clutching at straws, comes to mind
