you could try some redex injector treatment. if not get some from a cav sri 130 or something. if you have a multimeter check the resistance across the 2 pins on the injector, i think that engine is suppose to read about 16ohms on each injector, if its below 15 or above 17 then no good. and i think cav sri's are suppose to be 24 (check before taking out at scrappys.
they are noisy beggers, injector cleaner wont help i wouldnt have thought, petrol cleans better than that redex stuff anyway. if they are stupidly loud, then get another set from the scrappy and send them away to be ultrasonically cleaned then fit them.