From my dyno sheets the 3RZ's torque band drops off after 4000RPM's. As for your gas mileage, the reason it looks like you are getting great mileage is because your tires are smaller than your gearing calls for if you're trying to get back to stock on 5.29's. If you either drop gears to 4.88 or put on 37"s you'll notice a drop in the appearance of mileage.
