My latest experiment to see if I can increase MPG's is to add a spacer to the O2 sensor. Bought the spacer at Oreilly, it's actually called a Spark Plug Non-Fouler. Had to drill out the spacer for the O2 sensor to fit in.
Just put the spacer in today so I don't have MPG results yet. I have an 4 gas emission machine at my shop and after a 10 mile ECM reset the CO and HC readings dropped in half. The temp jumped about 1 letter higher and seems to have a bit more power. I am keeping an eye on it
, I'm a little afraid of leaning it out too much and cooking the motor.
I'll update this as I run some more test miles.