Geo metro 1.0 throttle body injector.
 

Does anyone know if there is a more efficient injector for the 1.0 3cyl g10 motor? Better atomization ?

How many degrees of timing are some of you guys running on the g10 motor?

I don't think there will be a unit that atomizes better, but you can improve vaporization rate with the one you have.

Adding heat to the intake manifold or to the intake air helps speed up vaporization. Adding a little Acetone to the fuel also usually helps with TBI or other wet-flow systems. There is a chance that a fuel heater may also help sometimes.

Higher air velocity around the throttle blade and lower TB bore increases fuel shearing and improves both atomization and vaporization. You achieve this by increasing signal (pull) from the engine while keeping the same sized port, or reducing the port size. You also do this when you throttle the engine, though the ports are still sized for WOT engine output.
Pull from engine can be increased by improving ring seal, total seal rings, etc..

Ports can be downsized by very carefully placed 2-part epoxy throughout the entire port to achieve a consistent cross-section area.

A performance valvejob will communicate more signal from the cylinder to the throttlebody. If your head needs refreshed, then there's an excuse to do it right.
More flow at the valve with the same size or smaller port means higher velocity in the port.

Sometimes atomization improves with injector cleaning or increasing the fuel pressure, but higher pressure increases flow and that can lead to idling problems unless you reduce the size of the injector. I'm not sure a smaller one is available for you.