The vacuum pump that GM used on the 6.5 turbo diesel was just enough pump for the waste gate, it didn't have any other purpose and was marginal. I don't know if the Duramax uses any vacuum controls. Just my 2c
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
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