I've got a 99 E300 in the shop that for all practical purposes runs out as it should but every now and then, after initial start, it will allow the boost to get to around 27 psi and then subsequent starts/operation the boost falls back to 21 to 22 psi max. There are no fault codes nor check engine light during either run so I'm thinking it meets all the required parameters to keep the light off.

During troubleshooting I notice that the solenoid that controls the turbo waste gate bleeds a slight amount of vacuum off to the vent while idling preventing the wastegate from closing off all the way there is approximately 3mm left till pulled all the way in. On my 98 E300 with the tune I do not see that bleed off during idle but I'm not really able to use it to compare to because of the tune. My question is should the wastegate be seeing full vacuum during idle all the time?

I've stated pressure in absolute so to 13 on mine and 7.5 on the '99.

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Jim