Looks fine to me, maybe the welds could do with a bit more rubbing down, but as you say it's an experiment.

Personally I love discoloured pipes, it shows that the machine has been used properly. If they were all pristine and shiny people might think it's a garage queen.

Tim H.
1986 4/4 VVTi Sport, 2002 LR Defender, 2022 Mini Cooper SE