Ah, those are the delivery valve holders.
The air incursion leak is probably at the union where the ball of injector hard line fitting attaches to the cup of the delivery valve holder.
To test:
1) on a cold engine - clean the area both ends of the hard line injectors throughly with brake cleaner and let them air dry completely.
2) test for dryness by touching the tip of a dry tissue to the union of the injector hard line flare fitting with the delivery valve holder.
3) if the fitting is completely dry - run the engine for a few minutes
4) shut engine off and re-test for seepage at the union with a dry tissue.
If you find a leaky flare nut fitting, just tighten it a bit more with your flare wrench (17mm?).
If the fitting still leaks after re-testing, then disconnect the line clamps securing one hard line to the other, then loosen the injector hard line flare nuts with your flare wrench and remove the suspect injector hard line completely.
Inspect the end of the injector hard line that seats on the delivery valve holder for any corrosion, scratches or deformations that would prevent a good seal from being established.
Clean, repair(polish) or replace any damaged injector hard lines.
Make sure to cover the open injectors and delivery valve holders to prevent foreign matter from being introduced.
On reassembly, carefully start the flare fittings by hand to avoid crossing the threads.
Once both ends of the injector hard line are loosely attached, press the hard line onto the delivery valve holder and hand tighten the flare fitting.
Do the same with the other end of the injector hard line at the injector on the engine.
After the flare nuts are as hand tight as you can get, then tighten the flare nut with your flare wrench to avoid rounding the flare nut.
Re-attach the line clamps.
Re-test to verify the leak(s) are gone.
Hope this helps.
