Any exhaust mod or change will result in a change in the way the engine runs. How picky you want to be about tuning it is up to you.
There are a couple of products you can use.
One type of system will allow you to download Pre-Sets to it. You go to their website, enter in your bike/engine, and the aftermarket parts you have newly installed. This only will be accurate if you have exactly the same aftermarket parts as listed for their pre-sets. You may have to settle for something close to what you have. This is the way to go if you're buying common over the shelf aftermarket parts, like Vance And Hines pipes.
Another system will allow you to program the way it works. For this you will need the bike take to the appropriate place that can work with the device, have the bike dynoed, then have them tweak the unit to what it needs to be. This is the way to go if you modify the exhaust, but also not a disadvantage if you use aftermarket parts as you can get very specific settings to your bike.
There are variations on either type of system, depending on the product selected. Some have dials that allow you to change the mapping on the side of the road (ie... swap to a mapping for higher altitude).
At the end of the day... you only need the retune it if you absolutely need or want peak performance, or if you are making a significant change (like fully open exhausts).
Modify them yourself. Costs you nothing. Better to try first, then to just go right out and spend money on a new V&H exhaust.
Here's what I can make a 250 sound like with simple modification
https://www.facebook.com/photo.php?v...type=2&theater
-- FYI... Cobra exhausts tend to be VERY loud. So maybe avoid if you only want a little bit louder.
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