318 MAX fuel economy builds?

If the goal is to save money you got to look at the gain and $$ reward of each mod.
Depending on yearly mileage savings per average mpg gain probably between $50-150, so say $100 savings per 1 mpg average gain, so you got to be careful with the cost, say you do intake carb ignition duals headers with a gain of 3 mpg depends how you go about it could take 2-5 years or more to break even.

First you got to figure out what each mpg gain will save you a year.
Second how many years do you plan using the car as a daily driver, if say 5 years your gonna want most mod to break even in a year or two.