Fuel economy

Use a gage and check fuel pressure. Not only check for correct pressure, check that the pressure holds and doesn't drop like a rock. I know some of the older GM throttle-body systems had an internal pressure bleed-off system, I don't believe you have that. Some of the national brand autostores used to loan out a fuel pressure gage. Other components can cause a fuel pressure issue, like fuel pressure regulator--leaking injectors.