[wrench]

water, BARR, PSI, etc. "The function is to increase the amount of vacuum and there by increase the amount of air forced into the compression chamber"

The term you are looking for is "manifold pressure". On a gasoline engine it is used to measure power setting of the engine, normally aspirated or turbo. The higher the MP, the higher the power setting. It is always a positive reading, but will be below atmospheric pressure on non turbo engines.

There is no such thing as "vacuum". Pressure, either above or below ambiant or atmospheric, is all still pressure and is measured in units such as inches of mercury, inches of water, BARR, PSI, etc.

My intake manifold is never below ambiant air pressure, and is often anywhere from 2 to 4 PSI above atmospheric pressure, this is the pressure the intake valves see, and is downstream from the turbocharger. The wastegate is closed at any MP below 15 PSI above atmospheric.

On the inlet side of the turbocharger, at speeds above 45mph, the front air scoop coupled with the ducting and large, free flowing air filter, produce at or slightly above atmospheric pressure. I have measured this area to get the ducting correct. The intake manifold has a pressure gauge on it at all times.

[org.whodat]

the front air scoop coupled with the ducting and large,

WE are not taking race cars here. Show me a picture of a stock diesel truck are car with a hood scoop. What happens with and on a race motor is completely different in varying degrees than on a stock car. Could you show me where a discussion about fuel efficiency went to race cars and motor.