P0203 Misfire cylinder 3

[tamarisk]

Having had issues with cold starting and diagnosed glow plug and fuel pressure regulator issues, I replaced all glowplugs, fuel filter and fuel pressure regulator.
Car now starts good as gold but is misfiring on cylinder 3, diagnosed P0203 Injector circuit malfunction cyl 3.
Very frustrating as previously when it did start it ran very smoothly. Have I somehow caused this problem with the work I've done?

I was wondering if I could swap the injectors around so as to see if the diagnostic code changes and I can narrow it down to the injector itself?

TBH I believe it to be the injector as I did the stethoscope test (or in my case a long screwdriver) and there is an audible difference in one.
Is it possible to clean injectors if blocked?
I really am not mechanically savvy, but with an ageing Megane I'm having to learn quickly.
Cheers!