I've got a 97 LS, and I beg to differ, I was getting about 25-26 mpg originally, then I put on AEM cold air intake, and holy shit, I was in heaven, I was getting 32 mpg, that and the difference in power was amazing, how much hp? I have no idea, but it made a world of difference to me. Then I just put on 4-2-1 headers, and that brought my mpg back down to about 29, 30 if i'm lucky, but its better than where i started, and the power difference is even better, but I don't normally romp on it constantly, i'm pretty gentle. Car drives a lot smoother now too, feels like when I first bought it