There are other paste-based metal polishes, but in my experience Solvol Autosol is easily the best. I also use Brasso from time to time on engine casings. It is less aggressive than Solvol, and comes as a tin of wadding soaked in Brasso, or in a bottle.
I understand that Exhaust bluing is a change in the chrome plate itself - it doesn't just affect the surface of the plating. It is part of the patina of age and use that bikes that get ridden on a regular basis will build up over time.