Any time you open up your exhaust it will increase horsepower, but decrease torque. So likely, your top speed will get a bump up, but you'll lose low end power, especially when starting from a stop in 1st gear. I'm THIS close to buying a growler supersport for my 08. Post a pic when you get it installed.Oh ive already bought the growler, just wondering if would help out on the top end? still awaiting it to be shipped.