Fun with Zeniths

[Nditiz1]

So I'm in the middle of tuning some 40 tins. I have noticed 2 things I need clarity on.

While going through checking jets and things I decided to pull out the air corrector over cylinder 5 as this cylinder is 2 kg/h less than banks 4 and 6. It had debris where the hole goes through it. I thought hey this is it! I then checked banks 4 and 6 just out of curiosity and found similar debris. Almost as though put there on purpose. Is this some method to make zeniths better?

2nd interesting item I need help with is the idle jet on bank 5. It is dead and I don't know why. If I remove it there is no change in idle speed. If I remove 4 or 6 there is a drop as it should be. I blew out the jet, shot cleaner in the port, but neither had the effect of making the idle jet do something. I ran out of time to run one more test after blowing air through that port. It shot fuel up through the main jet so hopefully that took care of any blockage. Any other tips?