Best way to prevent getting air in to the system?

Is there a CIS for the R2400, I cant find it on the IJM website?
I’m considering trying a CIS as a last resort to resolve my continuing problem with poor nozzle checks after refilling an ink cartridge.

After every re-fill of a cartridge (100% every time) I get poor nozzle checks often not just on the cartridge that has been refilled but on other cartridges. With 7 cartridges I am frequently re-filling and have wasted a good 70% of the ink purchased on trying to resolve this problem. I am using the vacuum method, is this the best way to prevent getting air in to the system?
Leaving the cartridge for 24hrs usually helps to improve the nozzle check, sometimes it takes a several days and head cleans each day to eventually get a good nozzle check.
Any help appreciated, I need to decide if I persevere with Piezo and reorder ink or go backwards to Epson’s ABW. I would much prefer the improved print quality and tonal control of Piezo K7,
cheers Stuart

We no longer offer CIS systems for the 2400.

The poor nozzles could be a sign of either faulty cartridges, dirty Capping station, print head and wiper blade OR a combo of both.

Please post an image of your nozzle check, this will help me determine where to next for your printer.

Also, a good cleaning wouldn’t hurt, here’s a video