Basically, headers help most anything, if the rest of the exhaust is done right as well. On lower performance builds, the gains might be modest, but they exist. The sound is a nice bonus.
Getting the exhaust out of the engine efficiently is never a bad thing, and doing it "better" is just a good thing to do in any case. Even the OEM's have trended to better exhaust systems over older "log manifold", horrid designs.
On my '87 Corvette, as most people know, the TPI induction system is designed to max out at a lowly 4500 rpms. Still, the car has a form of "headers" installed, from the factory. The point being, an efficient exhaust is good even for a low rpm engine.
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