i was thinkin about gettin a racing muffler for my 89 sentra but i dont really know a whole lot. i know it increases horsepower but not much else. does anyone have any recomendations for a pretty low cost one. also what else do these achieve other than horse power? how do racing mufflers affect fuel economy. do they make mufflers that increase the economy? if some could hook me up with info or give me some links that would be awesome. peace.