For all that asked for additional questions: I did not have the chance to go at the shop today for the details.. Sorry!
There is surface rust showing, but I haven't seen any crack/rust thru.
I have a sand blaster so I may clean them up to proof this. That will be a good project for next week as snow is moving over the South.
I need to also find the Stahl plate that came off from the headers. Since I moved twice, I misplaced it - so will give me something else to do in the snowpocalyse...
As far as comparing the 2 types of exhausts (Stahl on stock Vs Coupe King), I changed the exhaust system when I installed a M90 instead of the M30B30 - so I don't have a good comparison basis.
From what I read, installing larger diameter pipes such as coupeKing results in higher output but with a loss of torque in the low rpms.
There may be also a preference for some in having a regular steel exhaust rather than SS, as thicker steel seems to dampen some resonance/frequencies that some may not like. I have noticed that going from reg steel to stainless.:The exhaust notes from the original set up (Stahl on reg exhaust) sounded more 'matte' and less metallic.
I decided to go with CK as since I was planning to keep the car for a long time, I liked the idea of having it last.