Generally, the factory tune and exhaust setup is for overall rideability, reliability, emissions, and fuel economy. Changing the tune of a motorcycle can move it away from overall rideability. If all you want is better sound and a custom appearance, a slip-on is enough, and you generally do not need to change the engine tuning. For my '09 HD Sportster, just 100 USD on Amazon, some basic tools, and an hour transformed it from a wheezy Harley into a custom "rat rod" with a low grumble that seems to entertain young and old alike. At intersections, I get a lot of "thumbs up" often from the kids in the back seats of cars. It's not so loud that you cannot have a conversation with the admirers. If you want performance, on a motorcycle, even a few horsepower can feel significantly different. A few HP can be very expensive. So far on my Kawasaki Z900rs, a 10 hp increase has cost me 1000 USD. For me, that extra 10hp is worth it even though it can only be realized on a few isolated roads in the desert. It reduced my fuel range by A LOT! AZ does not currently enforce any emissions modifications on motorcycles and generally does not enforce most loud exhaust regulations. So, we have a huge range of options.