Yes, I have heard of them. Stebro has been around for a very long term doing stainless steel exhausts for European cars back into the 1960s.

Coming from New England, the salt on the roads would rust exhausts, particularly the mufflers, in one or two winters. Going with a stainless steel exhaust meant the exhaust lasted much longer plus the advantage of a better sound.

I am pretty sure I bought a stebro exhaust for an Opel GT years ago.

They have been around for a very long time - 50 years.