Honestly I get better MPG in sport mode at highway speeds locked into 8th gear. The 3.73 makes rpms too low and boost numbers too high to maintain highway speeds to maximize mpg. Drivability is fine though, the bronco has plenty of pep. I would 100% swing for the locked rear and upgrade gear ratio.
Sports mode gives me the best mpg. The higher rpms keep the engine from lugging and it does not get into boost to maintain certain speeds. Low RPMs and higher boost numbers are what kills my mpgs.
This is what I got.
https://www.stage3motorsports.com/m-1830-fpac-ford-ford-performance-arb-portable-air-compressor.html
Its identical to the ARB one for $400+. the box is really nice to carry around and it works so well. I was worried long term about the NAPA ones even though they may air up...