Volvo d12 fuel problems injector cups

This is the problem, it started with the diesel mixing into the water, I took it to a mechanic and was told it was injector sleeves cups, I changed them and now the motor won't run smoothly it will turn off after a minute. It gets air in the fuel lines. We have checked the lines but can't find were it's coming from. The truck was running perfectly before changing the sleeve caps. Any suggestions, please help. Injector caps not exactly the same, dealer said it was an upgrade and that the originals are no longer made. Thanks for reading my post