Draw-through carb info?

I'm not sure about other carbs, but with the Holley you need to have a separate intake vacuum/pressure line from the intake manifold to the carb. The stock Holley senses intake vacuum from the base of the carb. When used as Draw thru, it is possible for the base of the carb to "see" vacuum even if on boost if the throttle is only partly open. In that case the power valve might not open and the carb will be lean. Found that out the hard way. I used a 500 holley 2 bble on a Rajay F60 turbo on a 65 valiant 170 slant six.