my milltek pipes are brown and nasty . and the system is overall poor quality . rust on the welds of the back box . down pipe brackets and naff and keep breaking .
....What I don't understand is how TIG welds and stainless steel rusts. Downpipe brackets certainly have been a problem (including once on mine) but Milltek have done things to reduce that problem some time ago. A remapped car on OEM engine mounts is more prone to the kind of movements which can cause breakages and that is why a poly torque arm insert is included with each new exhaust system.
Tarnishing is perhaps inevitable considering the heat temperatures stainless steel exhausts endure, but surely tarnishing is far more acceptable than the rust an OEM system might suffer from.
Eitherway, each of us has different expectations and I can only say that I have had several years of good experience of Milltek exhaust systems and the performance and sound far outweighs the problems.