Injector leak test

[Peterbilt387]

Hello,i have a PETERBILT 387 with isx 2008,i did the leak test and i found between Aand B bubbles, i replaced injector number 3. Everything fine,i was driving the truck for a pick-up and back to my yard,i left the engine to idle for 3 minutes and start shaking the engine and worst then befor to replace the 3th injector. Did again the leak test and i got bubbles again but now i didn't bar it to find out exactly witch one is leaking.when i did the first time leak test it was leaking only between A and B.thank you in advance