Hello AquaTune, I bought your AquaTune system for my '89 Chevy Suburban, 5.7L, 4-wheel drive. This is the 1500 series. With this gas hog I was lucky to get 14 mpg on the highway. Now I am totally beyond myself because on my last trip I got a whopping 28 mpg! You can best believe I've been telling everyone about this product.