Also on an 03, I went the other way. Had the OEM exhausts and added the 16GA Double Barrels.
I installed the 16GA exhausts and the K&N high flow air filter. I purchased the powervision tuner and flashed it using the tune they provided.
Apart from tuning the bike for the new exhaust there is not much else needed. Just be sure you get the OEM bracket hardware as the mount that the 16GA uses is different to the OEM one. Hope that helps.
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