So... any more ideas?
Have now replaced the following:
-Walbro with another new Walbro
-Crank angle sensor
-Made sure there's no rusty grounds for fuel pump wiring (apparently common issue).
-Removed the one way valve on MAP sensor (car's only running 12psi now anyway so fuel cut not an issue)
-Plugged in my old (known working) W6 ECU
and it's still cutting
Please someone give me more ideas before I push it off a cliff!
Could bad air flow meter do this? mine looks pretty good, and was sprayed with AFM cleaner not long ago.