G-Sync Emulation Settings

[Ed Oscuro]

You are sure you have G-SYNC working in other cases?
Also double check your nVidia Control Panel and look for an entry here: Display -> Set up G-SYNC. Make sure "Enable G-SYNC" is selected, and try selecting "Enable G-SYNC for windowed and fullscreen mode." I do not think it should matter if MAME is running in a traditional exclusive fullscreen mode, but it's probably worth checking anyhow.

In some rare cases I have noticed tearing on screen (usually after taking a screenshot in the PC game Rage, but some other game I played with had some persistent tearing until I fiddled with some setting or other). Usually it "just works."

MAME .106 is a years-old MAME revision. With any luck you should still have a choice of different renderers, like DirectX and OpenGL, maybe SDL as well.

If you're not committed to that particular revision, it might be a good time to upgrade to a new MAME version, and get better compatibility / more games in most every case. If you have a PC that can deal with G-SYNC then it should handle most games in MAME with no problems.
If setting up command line MAME is difficult, there are lots of releases with built-in GUIs, even ones that old.

I also think it's worth noting that Windows 10 should give the best performance in MAME and G-SYNC, perhaps only by a tiny bit. If you have an operating system that would have qualified for the Win10 free update, you may still be able to get it.

There are other possibilities still but you haven't given enough details and I don't want to waste my / your time on dead ends.