I have purchased and installed a Poweraid tb spacer on my '92 4.0l. Although i haven't calculated the mpg's yet there is a noticeable low-end power gain. Also to the po, the main areas to better fuel mileage are weight, wind drag, maintenance, gearing, and choice engine mods. One mod that no one has mentioned is converting to electric fans and deleting the mechanical. Logic would make one think that would take strain off the engine, therefore better mpgs, lower engine temps, longer engine life. Also less aggressive tires should help in your pursuit of leaving more gas stations behind.