Diesels do not incur vacuum...ie negative pressure in the manifold since they have no throttle plates. On gas motors when the turbo is spun up and the driver lets off the gas the turbo continues to spin...as it does in a diesel, but the flow hits a closed throttle plate. This causes the pressure to come back at the compressor wheel. The manifold is now negative. Unless a pop off valve...not a wastegate is employed all boost is loss and the car is as flat as a board when the driver gets back on the gas. Monitoring the negative vacuum allows proper setup of the pop off valve. Purchasing a gauge which reads negative manifold pressure for a diesel is not necessary. Buy a 0-60 and you will be fine for all your needs...unless you have really BIG plans.