The engine looks good Mark👍
One time, with silvery parts like those, I got cool results by spraying very light misting of black paint through the airbrush ... just super light passes and not getting too close with it ... mostly it just dirties the surface appearance to whatever extent you want to go, and I suppose that using matte black would also dull out the sheen a bit, but if you were to do it you might want to remove the headers so they could be done separately, or not at all.