I have a 00' v6 stang with 66,000 miles on it, my mileage has been down the drain recently. I'm going to get a tune-up at pep boys, I think some problems that might be contributing for my poor mileage are: Dirty injectors, dirty fuel filters, old sparkplugs and wires, and bad o2 sensors. Also, I am thinking about replacing my cats since they are restrictive and/or clogged. Anybody have suggestion where I can find a good set? Btw I would have to remove the Y-pipe right where the headers end right? I am getting GT takeoffs soon, will the takeoffs bolt on to the cats?