It is easily done, but also easy to do wrong.

The little box you have replaced is an Electro magnetic fuel pressure actuator. The black ecu u can see behind the heater box takes inputs from all the sensors in the engine bay. It then sends a signal to the EMFPA which varies the fuel pressure depending on engine and driving conditions.

It works by increasing or decreasing from a base fuel pressure. This base fuel pressure can be adjusted, and is different for prerry much every car/EMFPA. So you have fitted one of another car, and it's not right for yours.

Without fuel monitoring equipment, you never know what your actually adjusting to, which is never a good thing. The EMFPA actuator adjusts the fuelling across the whole of the rev range. There is also a 3mm allen screw by the metering head, which adjusts justs the idle fuelling. The car is not firing probably because the mixture is too lean.

Before you try adjusting anything, you should do a simple test. Take the airfilter off, and you will see the metering flap. Push it - it should move down an inch or so.

Now, get someone to crank over the engine. You should see this flap moving up and down a few mm. If it doesn't - the car will never start, and you have an air leak somewhere. If it is pulsing, then while someone is cranking, push it down a little more. I mean a LITTLE, it's very sensitive. If the car starts, or at least tries too, it means that your idle mixture is too weak.