Nothing really out there. Toyota encodes their software and doesn't let anyone in. Unichip makes piggyback ECUs that work with the stock ECU. Bully Dog is just now coming out with a GT Tuner for the first later trucks. Let's see if it even does anything. Chips are a thing of the past. I believe flashable EPROM chips were dropped from engine ECUs in the early 90s.
More power - Forced induction or buy a sports car. Gears will make your truck accelerate faster but higher MPGs will suffer.
Better MPGs - Right foot mod or sell for a 4 banger car.