Switch-Over-Valves..they control the EGR and AIR systems.....
Under the front engine cover,,at the end of that white plastic vac line that is Notorious for cracking..

" OK Alex,....Let's see ...I think I'll try " Benz Diagnostics Oddities" for $600....

'"Um...What IS ...SOVs ?? "

Ding -Ding -Ding ..."Correct..SOV !!!!! "

"Um..Ok, Alex.... let's stay with Benz for $800"

Clue is .."OVP"

" OVP- OVP ...uum...... " What is Over Valve Protector??? "

Auuugha..Auuuugha..!!!!!!!!!!

No, No..sorry..we were looking for "Miter Box..Miter Box"...sorry

"Damn ....."

__________________
A Dalton