about the fuel pressure..here is some reading.
What i meant is this..sometimes when people remove the engine they plug the fuel line with some kind of plugs. Then when the fuel is connected the plug stays - or is forgotten that will create to big of a fuel pressure ,symptoms car starts and then dies.
Also did you recheck position of your TDC distributor rotor facing no.1 cylinder.
And one more thing the ground strap on cyl number 1 intake.
Ivan
https://www.porscherepair.us/porsche-911-1984-1989/fuel-supply.html