You can remove the mixer housing to get a better view, and use some baling wire or something similar to hold the flap wide open. Then just block the vacuum signal to the actuator, and reinstall the housing. You should do the same for the EGR while you're at it. Since you have black smoke, I'd be more concerned that your wastegate isn't receiving a proper vacuum signal, which may be preventing the turbo from building up sufficient boost.
I removed the entire EGR mixer housing from my 602 and converted the turbo over to a pressure signal wastegate actuator from a 603. By doing this, I have eliminated a significant number of potential problem areas and simplified the vacuum requirements. Here's the basic vacuum routing needed on the single cam diesel engines.
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I removed the entire EGR mixer housing from my 602 and converted the turbo over to a pressure signal wastegate actuator from a 603. By doing this, I have eliminated a significant number of potential problem areas and simplified the vacuum requirements. Here's the basic vacuum routing needed on the single cam diesel engines.
