Take your .sav file, reName it to the samething your Ez-flash iv calls it, put it in the saver folder and click overwrite.
I play roms on my DSTWO and No$GBA, when I want to play on my Ez-flash, I just look at that the ezclient named it (i'm not sure why but if I have a fireRed.gba file, when the ezClient adds it it changes it to something like Pokemon - Fire Red.gab I think it's just reading something out of the meta data, but w/e if it works it's good. I just don't like the long file name on my computer, old habbit, camelCasing is an old habbit too). Anyway so I take my fireRed.sav off of the DSTWO or out of the folder No$GBA is using, I rename it to what it's called on the EZ-Flash. In this case I rename it to "Pokemon - Fire Red.sav" no quotes. Copy that to the saver folder (it might be all upper, SAVER, either way that folder)on my ez-flash and when the game boots it loads that save file.
What happens when you shut your EZ flash off is it stores the games save state somewhere on the card (not sure what part of the cards memory) using the battery, when you turn on; that message, "hold L to skip saving" what it's doing is over writing the save file. So if you do it, the card knows no difference and boots w/e save file it has. Just make sure you were not playing that game last. Like if you were playing fire red. Turn on your system. Let it do it's saving dance. Then shut off and put yoru microSD/miniSD into your computer, and over write it with the save file you want.
I've done this b4. Playing fire red. Want my DSTWO's save on it. Copy that over, overWrite. Turn on EZ-flash, it starts overWriting the save I put on with the save it was storing to write when it turned back on >_< Took me a few tries to figure it out.