Yes and no to the needing custom tunes for the extra exhaust you do not have to have it but you will be able to take full advantage with a tune.
All newer and older carbed vehicles are like this some manufacturers will see the extra power and detune to make the factory power after adding bolt-ons (Subaru is the worse)
Oh some food for thought if anyone is looking at making some big power #'s later on testing different collector lengths primary lengths etc can help get the last little bit f power out of the motor. (NASCAR guys are playing with them)
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