Jack has you covered as far as trying to get straight pipes to work. If you're looking for your bike to be loud the straight pipes will do that, but if your looking for peak performance you need to think about another style of exhaust. There are fishtail type exhaust that are not straight pipes, but they do cost a little more. I tried a set of straight Porker pipes on my 80ci. I never got it really dialed in but it would run fast. The biggest problem I had was that none of my riding buddies would ride behind me. Just too loud.