what is OEM name for 540i BMW 1997 Model Catalytic converter right side?
Is it Miller or D.E.C . I was told both are not..If they are so please
let me know as well..Please confirm the
right OEM for 540i BMW 1997 Model Catalytic converter right side..

I assume you're asking this question because you live in California,
need to replace your cataltic converter and were told you cannot use
an aftermarket part.
   This link might help: http://www.convertergeek.com/california.html.
   They offer genuine rebuilt converters with a warranty in an exchange program.  
   Perhaps this will be of some use.
   Have a good day.