Local story from the 70s
Two mates got together. One had a small tyre & exhaust garage in Bolton, the other galvanised gates and fences.
The second chap developed a technique of galvanising the whole exhaust, inside and out. The first started selling them in the garage at a fraction of the cost of SS with a life of the car guarantee.
They got an offer they couldn't refuse from a large exhaust manufacturing company and the whole thing was shut down, never to be heared of again.
I wonder why?
I also remember a chap on Tomorrow's World who designed a car oil filter that was so efficient you would never have to change your oil again. It must have been like the ones large ships use that just purifies and recycles engine oil over and over again.
Then again a plastic exhaust is possible. Or at least the centre and back sections. Probably a lot quieter too.
Its a copis...... Conspri....... Conspinter....... Oh, someone's avin a laugh.