With some DTIs you can get fault codes without connecting up to diagnostics, you can then google the codes
brake and throttle pedal to the floor then turn on the ignition a click or two until the engine management light comes on (but DON’T start the engine). If it works then the car/spanner light will blink the code(s), have someone with you with a pen and paper as they flash out pretty fast. 3 flashes then nothing means no faults reported, but a long sequence of flashes and gaps is a fault code
one flash for one, two flashes for two etc, ten flashes for zero, the codes are all 4 digits long
Google any codes extensively as they can be a red herring.
Which bit of electronics have you had replaced? – theres one on top of the engine (ECU – about £200 for a refurbed/exchanged one) and one on the back of the fuel pump, tucked down behind the engine (EDU about £40 for a refurb)
The latter controls the fuel pump only and a bad solder can cause the pump to stop intermittently or completely.
The one on the top of the engine is vulnerable for fuel seeping through the wiring loom into the electronics – disconnect the leads and see if its wet inside. If you are getting a bunch of different codes that can indicate this box being fuel damaged