C270 W203 Catalytic converter

[HelpThisDude]

Hello all.
My C270’s (W203) catalytic converter, (the one under the pass compartment) has been rattling always for a while.
When I enquired on changing it, I was informed that I had to change both converters, as the cat near the turbo would have caused the lower one to fail.
Is this true?

Cheers

 

[type49]

Possibly. The front cat is more likely to fail but you can't tell unless you remove them both