Citreon Relay 2.2 transit duratorq engine?

Hi, is there a mechanic on here who could advise me on the van listed above ^

Had van 8 years and recently an injector went down clanged like mad so I bought some second hand injectors had all 4 re programmed ( i know you will say that was a bad idea) but engine has started missing sounding abit clangy is this a sign off a injector not fully functioning? Also on diagnostic i am
Getting low airflow volume any advice on them two questions will be very appreciated, thanks mark