I just bought a pair of Flowmaster original 40 series mufflers for my Olds, and I was wondering if the sound of them will be altered in any way by the fact that she still has her stock manifolds as opposed to headers. She's not a quiet car in the first place, even with her stock mufflers, and has "true" dual exhaust, but I heard the manifolds can change the sound. I'm not sure if this is true, but I am hoping someone here can offer some advice/opinions! I have heard these mufflers on other cars, and they are LOUD, which is what I wanted, anyway...