(mmmmm. Bowmore Islay malt)
Forget the injector cleaner, it'll take forever. Tip 100ml of pure acetone in the tank.
no point trying to add addatives or change ecu chips etc to gain more power for this make of engine. keep it std for reliability. If you think the No.1 injector has a problem it should thorw up a check engine light. the other thing is to measure the resistance across the connector pins (ohms), I can't fully remember but if the resistance is higher than 110ohms then it will flag an error. I fooled mine by putting a resistor in line but be aware that the wires do go brittle over time. Another option is to take the injectors out and get them cleaned. A diesel specialist should charge too much plus they will check the "pop" pressure so that they can see if they are all operating the same. The No.1 has the flying lead so the socket needs to have a hole in the side (make your own) but be careful not to allow the socket to slip as it will cut the wire in two