[dont]

I replaced the stock SPF 2.5" with 3" x 20" cobra packs with the louvers facing the air flow. The fluttering sound is brief and only when I depress the clutch for gear changes. The over all sound is deeper but louder under hard acceleration. My dyno results were 15hp and 16tq gains on the same dyno with almost identical weather conditions. The only thing that I would do different would be to change the collectors for a smoother air flow. My engine is a 460 BB.