Pratt, If you are debating on buying a new exhaust, do that before buying a PC and having a tune done. In most cases you do not need a PC when adding an exhaust. However if you mess with the air flow that's when the PC (or other a/f module) is needed. So to recap. 1. buy new exhaust 2. install said exhaust 3. purchase PC, or other fuel processor module. 4. install module 5. get tune completed. The PC runs around $250 - $350 depending on bike and where it is purchased. The dyno tune is usually around $300.00 again more or less expensive depending on where is is done. The PC usually will increase HP and fuel mileage, and just make the bike run a little better. There are maps you can download from power commanders website, you can also find them on exhaust websites. However, there are slight variances between bikes and if you are going to spend the money on a power commander then you might as well spend the extra money to have it tuned to your specific bike and setup.