If it is an electrical issue, sounds like 1 off 3 possible things to me...
(in order of cost - cheapest first)

1) Coolant temperature sensor or wiring to sensor failure.

2) MAP sensor.

3) ECU Chip is based on old version weber software.
(This excludes Pectel board chips)
Early version original Ford P8 chips INCLUDING modified/remapped chips suffer from starting issues randomly.
This is quite common on some cars and usually manifests itself as bad starting
requiring a few starting cycles before it starts perfectly.
As a test, If the car starts up badly or takes more than 3 seconds to start, switch it off straight away, wait 10 seconds and try again a few times.
This is caused by a manufacturer (WEBER) software bug that reads parts of the
unused ecu memory which will have random data on switch on.
Over time, age and temperature this problem can appear/disappear randomly or
appear nad never go away.

Just a few suggestions