If the same nozzles are missing in each nozzle check, then you are dealing with something in or on the print head (a clogged nozzle), rather that air- which move around to different nozzles.
You can do many repairs yourself (provided you have the ability to thoroughly read + follow instructions, have patience to work with small pieces, and give yourself enough time so you're not rushing), by following repair procedures in the Epson 4900 Service Manual, which you can get online (I get repair manuals for all our various Epson printer models from www.2manuals.com). I know there are many places to get replacement printer parts online, and I typically get parts from www.compassmicro.com that we don't carry (we mainly just carry dampers, wiper blades and cutter blades), though I just checked and see they only have three parts listed for the 4900- including the "Pump Unit", which includes the pump, flushing box, capping station, wiper blade and wiper blade cleaner all in one easy to replace unit. They also carry the damper assembly ("selector unit"). You may be able to find the wiper blade separately elsewhere.
As soon as I have the time, I need to work on our 4900, which I believe needs a new pump.... When I work on the 4900, I will photograph and record the procedure to help others gain knowledge and confidence in working on their own printers.
I hope this helps, best regards~ Dana