w129 with w230 kit lequrish all sorts and non runner

[dinoy]

Mercedes Benz SL 500 silver 69500 Miles Spares or Repair Full Service History | eBay

is it true the cat at fault anybody nows

 

[Doodle]

I doubt the cat has anything to do with it. More likely a crank or cam position sensor failing once the engine is hot.