I have an 08 si coupe that has about 60,000 miles on it. I am pretty much finished with cosmetics, but I am now ready to start under the hood. I drive about 100 miles a day, so I am wanting to retain as much gas mileage as possible. I am just wanting to be able to hang with some of the stock 5.0s or better....in the end, gas mileage isn't that important I guess. I don't want to crack the block, just wondering about some bolt ons....definitely no loud exhaust...much appreciation.......Swink