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terrasmak said:
Bolt on is just for noise and looks ,while the full system will give you more power .
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When you guys say "bolt on", you mean an aftermarket slip-on can, right? Just an aftermarket exhaust can, when your bike is remapped, will give you more power because it is allowing the engine to be a more efficiant air pump. Stock exhaust cans have baffling in them that slows down how fast the exhaust can flow out. Aftermarket exhaust cans are straight through cans (at least the good one are, if it's not a straight through can, then what's the point?) Since the air can flow freely out of the exhaust can, you can remap your bike to have it pull in more gas and air since it can now push more out.
You can get a little more power out of a full system compared to a slip-on because aftermarket headers are sometimes slightly bigger and are bent differently to promote better flow. But regardless, unless you remap, you won't get much improvement besides noise.