Looking at an 05 s convertible jcw. 80k for miles. I ran vin thru a decoder and didn't see jcw as an option.?. Was it an option or was the jcw kit in 05 dealer installed in all 05s.

 

The factory JCW option occurred for the 06 model on both the R53 and R52. This option included the LSD so on the 05 the LSD would be a different factory option

 

in 05 it could come either way Factory or Dealer installed.

If it came factory it would have the LSD and JCW brake kit. If it was dealer installed they would have had to order the LSD as an alone option from the factory, and also pay for a JCW brake kit if they wanted those in addition to the JCW tuning kit

 

On the 05 pretty sure the option was not a factory build until late in the model year. The VIN will determine whether it is a factory or a dealer install.