When loosing power comes as a pair,
There is something to be aware:
If the sum adds up to five,
Sparky bits may not be live.
If the loss is even or odd,
Loss of fuel may be the sod.
It is not uncommon to have pairs of cylinders not producing power. Once you have determined which pair of cylinders is having the problem the diagnosis becomes much easier. For a turbo car the:
The ignition coils are common between cylinders - 1&4 and 2&3
Diagnosis of the ignition system can be done by switching around the plug wires to see if the problem moves with the wires. If so it is a problem with the wires. Although having two bad wires is uncommon it is not unheard of. The next step is swapping the coil packs to see if the problem moves. If so it is a problem with a coil pack. If neither of the tests moves the problem it can be the coil pack base. This is a much more expensive part.
The fuel injector electrics are common between cylinders - 1&3 and 2&4
Dirty contacts in the connector IHC - B5 can be the problem. Also check the resistance of each injector (1.8 to 2.2 ohms but remember to subtract the resistance of the measuring leads). They should all be the same. One bad injector can cause the injector circuit in the ECU to fail (overheat) shutting down both injectors on the circuit. There will be noticeable improvement if the electrical connector of a bad injector is removed whereas removing the connection from a good injector paired with a bad injector will probably make no difference.
There is a theory that an apparent electrical failure is due to a mechanical failure: If an injector sticks then the solenoid core may saturate earlier than normal thereby giving a lower impedance which the ECU cannot drive. This theory is based on the dc resistance of a bad injector being no different to a good injector, but has yet to be verified by trying to un-stick the pintle.