I have sidepipes that were coated black by HPC back in 1992/93 here in CT. The guys at HPC started their own firm called Airborn Coatings. They also do silver sidepipes. Here is their website...
Check out the website:
http://www.airborncoatings.com/
As you can see from their website, Airborn does a great deal of work for serious professional racers. They do a great job and do most of the coating work for ERA from what I have been told. take a look at the exhaust headers in silver on the "customer" website. The coating is so good it looks like polished aluminum but it is heat resistant and stays that way. Quite nice indeed.
My sidepipes are about 12 years old now. Still matte and lusterous black without any chips, rust or rot. A better job you cannot ask for. Darned good coating. Additionally, my Sidewinder intake manifold was done in the Silver Aluminum coating and it looks like fully polished brand new aluminum even after all these years.
On the ERA GT-40 Airborn does all of the control arms and sway bars in silver and they look just super. So good in fact, I was thinking of having my sway bars done by them next winter season.