I have the 3.07 rear gears, a NA om606 with a 6mm pump, timing advanced probably more than it should be, full 3.5 inch exhuast turbo back and a very low restriction intake setup. Car makes 2-3 psi on highway traveling 75-85mph. I get around 34mpg driving fairly aggressively. Your mileage may vary. I am looking into a 6l80e or 4l80e swap in the very near future. I hate the 722.6 transmission. converter never locks up etc.