I replaced a solid roller with a solid roller and yes, the car was much faster when it had headers on it.
With hooker super comps, slicks and 3" exhaust the car ran an 11.78 @ 118mph.
With the only changes being HP manifolds, 2.5" TTI exhaust and re-pop E70-14s, the car dropped to a 13.2 @ 105mph. (That was one outing at the track and my times were horribly inconsistent. Launching on the E70-14s with a 4 speed isn't easy.)