How do you test the Solenoids that control the EGR and Turbo wastegate?
 

These two leak vacuum applied via a tester when not actuated in my son's E300d. Shouldn't they hold until given 12V activate signal?

EDIT to add findings:
I pulled both solenoids part 000 545 04 27 or 0005450427 and found that they leak from the supply side to the side that feeds the wastegate or EGR without 12V applied. The turbo wastegate actuator solenoid leaks very badly but both leak.

It should only allow flow with 12v applied as far as I can tell. So I think they're both bad. At the least they are different as in one flows much more than the other without a 12V signal. Pretty sure that's why he's getting the PO243 code.