Did try a project/experiment with using a exhaust valve dummy simulator to keep the single exhaust valve open on a C257.

I am NOT getting a CEL but after running a code reader, getting code: P140487: ("Exhaust flap 2 has a malfunction. The message is missing") that I can clear out be reappears immediately afterwards.

Can't say I "feel" anything different in the car but from research, it seems to sometimes put C53's/C63's in a soft limp mode.

Question is, in ours, will this stored code be a problem or will something be obvious if it goes into a soft limp mode, given no other codes are present ?

Thanks.