+1 ^^^
Fuel injection systems are not like carbs, i.e. changing "jets" to set fuel flow, and even that doesn't work, lol.
Gasoline engine needs 14.7:1 air:fuel ratio, and that is a WEIGHT ratio not volume(why "pre-vaporizers" are hooey)
14.7 POUNDS of AIR to 1 POUND of gasoline
14.7 grams of air to 1 gram of gasoline
WEIGHT ratio
Fuel injection gets better MPG because it can do real time adjustments to that ratio, but it needs good information to do that.
Clean MAF sensor
Good O2 sensors
Good ECT sensor
Working thermostat that keeps engine coolant at 190-200degF, under 190degF lowers MPG
Also never shift to Neutral when going down hill, while this was helpful with Carbs it actually costs you fuel with fuel injection
Computer can turn off the fuel injectors, 0 fuel being used, when going down hill in gear
If Speedometer is above 5MPH and RPMs are above 1,500 and throttle is closed(foot off the gas pedal) then computer shuts of injectors, so going down hill in gear is 0 fuel use.
Computer is set up for stock injectors and stock fuel pressure, so it knows how many grams of gasoline will flow from each injector when it opens it, for say 100ms(milliseconds)
If you put in larger or smaller injectors all that will happen is that the computer will have to open them less or more that 100ms to get the same grams of fuel
Best case is that you won't notice any change at all
Worst case is that CEL(check engine light) will come on with Rich or Lean codes because computers calculated Open Time for the injectors is no longer correct.
Rich and Lean codes come from fuel injector open time calculations being off
Which can be caused by air leaks, low fuel pressure, failing sensor or wrong size injectors
Watch spark plug tips, if they are getting a darker color then engine is running Richer, if O2 sensors are over 80k miles then replace them