I think you are far more likely to notice a difference with a modified engine. That said, I have headers on both a nearly stock 3.0CS and also on a second with a Korman stage 2 3.0 (230 hp on dyno when new, long ago.) Yes, they are noisier and yes they do rust eventually. Another option for a larger inner diameter exhaust manifold is to go to the E-24/E-28 3.5 engine manifolds. I'm not sure that they have the same downpipe flanges, tho. Perhaps, someone else here knows.