It's a 2008 Chevrolet Avalanche 5.3 Liter V8. I love the truck even though i only bought it because i needed something to haul stuff around in and didn't think an SUV would work for what i needed, and it has the engine that shuts down 4 cylinders while cruising. I think it's called active fuel management so gas mileage isn't horrible, but i wonder what i could do to make it better while getting better horsepower as well. Any ideas? Brands and prices included please?