Hi, I have a a6 2.5 tdi 2004 with the bdg engine. Car starts eventually but the smoke is something else! Car also heavy vibration at idle. Removed injectors to clean. stripped injectors of its internal components. question is i have 4 injectors which all components came out ( 2 springs and a copper collet and washer and needle) see pic and 2 which only released 1 spring and needle. Would i be right to thing i either have 2 good injectors or 4 bad ones. Also if bad can i use a injector with a different end letter and just change nozzles over.