As far as I'm aware it makes no difference, but I would have thought if it is anything like real life you would tune the car for N/A power and then install one of the forced induction options. After that then you would install the ECU as that would control the engine management and installing it after all the upgrades, in real life, would leave your engine more powerful than if you put it on before you tuned the engine.
Then I think you have to run the car in, for how long I don't know, but that is what should give you the most power.
(Do an engine rebuild first if the car is 10-15+ years old or if the car is high mileage, otherwise don't bother with one)