Cat c15 mbn knock

Hello everyone looking for help with my 04 Pete 379 with c15 mbn I have a weird knock around cylinder 6. At light throttle n low rpms it knocks/rattles and at idle. If I give it lots of throttle or pull a load I don’t hear it unless I’m at light throttle low rpms. No smoke really just a bit of black when up lshifting. Sometimes it seems like it’s missing then next minute seems ok n smooth at idle,looking for a little help before I bite the bullet n take to the shop, also the noise sounds like it’s in the combustion chamber area and I took valve cover off and nothing is broken or loose up their

 

I haven’t tried that, but I will now thanks

 

Update: I took off valve cover and unplugged #6 injector and the knock goes away, does that most likely mean it’s the injector? Can I swap another injector into that hole say from cylinder 1 to see if the noise moves to that cylinder?