My understanding is that the higher the number the more vacuum therefore the middle cylinder showing a lower vacuum could indicate a leak.

You have that backwards - higher number is LESS vacuum (i.e. higher pressure)
The cylinder pulling 540 has BETTER vacuum (lower pressure) than the other two.
Why are they different?
Because the balance screws adjust the relative 'closed' position of the throttles (they are not really closed - if they were, there would be no airflow at all and the engine would stall)
The one with 540 has the throttle 'more closed' than the other two. (or conversely the other two are 'more open')

At sea level pressure is ~ 1013 hPa (or mbar) - if you go to say 5000' (colorado for example) then atm pressure is ~ 840 hPa
At 10,000', atm pressure is ~700 hPa
Altitude above Sea Level and Air Pressure

At idle, the throttles are closed, therefor it creates a low pressure in the throttle bodies as the pistons pull against them;
when you open the throttle, it lets air in so the pressure will try to normalize to that above the throttle.
The highest vacuum, (lowest number) will be if you rev the engine then close the throttles - this creates a higher excavation rate of air from the area below the throttles, therefor the pressure drops.
 
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Yes. Adjust the #1 (front) and #3 (rear) clyinders to match the values of #2 (middle). Warm idle if you live near sea level should be around 540 ish.

Within 10 is fine, so if at idle
530
540
540

its close enough.
 
You have that backwards - higher number is LESS vacuum (i.e. higher pressure)
The cylinder pulling 540 has BETTER vacuum (lower pressure) than the other two.
Why are they different?
Because the balance screws adjust the relative 'closed' position of the throttles (they are not really closed - if they were, there would be no airflow at all and the engine would stall)
The one with 540 has the throttle 'more closed' than the other two. (or conversely the other two are 'more open')

At sea level pressure is ~ 1013 hPa (or mbar) - if you go to say 5000' (colorado for example) then atm pressure is ~ 840 hPa
At 10,000', atm pressure is ~700 hPa
Altitude above Sea Level and Air Pressure

At idle, the throttles are closed, therefor it creates a low pressure in the throttle bodies as the pistons pull against them;
when you open the throttle, it lets air in so the pressure will try to normalize to that above the throttle.
The highest vacuum, (lowest number) will be if you rev the engine then close the throttles - this creates a higher excavation rate of air from the area below the throttles, therefor the pressure drops.
If you watch the video that R-III-R Turbo posted you will see that as the engine is revved i.e. the throttle is opened the numbers drop as the vacuum decreases? Would this not indicate that a lower number equates to lesser vacuum?
 
No, what you're seeing in the video is ECU reporting lag. When he blips the throttle it takes a second for the ECU to update the screen, by the time it updates, its getting data from the decel, so the number is lower because its a closed throttle on a down spinning motor.

Look at my posts with pictures, they clearly show irrefutably that open throttle = higher number = more air pressure = less vacuum.

Not sure how I can possibly show it more clearly than that data log.
 
Ask yourself this: What does MAP stand for anyways?

Answer: MAP sensor - Wikipedia, the free encyclopedia

The ABSOLUTE part is what makes it a MAP and not just a Vacuum sensor. There is a difference.

All speed density systems do this the same, they all use absolute, if they didn't they couldn't compensate for elevation changes.
 
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MAP signals are transitory, not static. 10% throttle at any RPM isn't a set map value, 20% isn't a set map value etc. As the RPM go up, and the engine stabilizes at a specific load the MAP signal will be a lower number. You need the engine under load to see accurate values, a free wheeling motor changes MAP values too fast for TuneECU to capture.

Look at my datalog snap shot, it CLEARLY shows 940 MAP signal at WOT and 270 at close throttle run down of the motor. 0 MAP signal would be pure vacuum, absolute not relative.

MAP = Manifold Absolute Pressure, by it's very definition, the sensor is an absolute sensor.

14 years tuning Speed Density systems both NA and FI, I'm 100% positive its an absolute sensor the value of which increases in value with throttle opening.

This is one of the dangers of TuneECU, it's limitations are significant because of the reporting speed of the Keihin setup, and can easily give false impressions of things.
 
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MAP signals are transitory, not static. 10% throttle at any RPM isn't a set map value, 20% isn't a set map value etc. As the RPM go up, and the engine stabilizes at a specific load the MAP signal will be a lower number. You need the engine under load to see accurate values, a free wheeling motor changes MAP values too fast for TuneECU to capture.

Look at my datalog snap shot, it CLEARLY shows 940 MAP signal at WOT and 270 at close throttle run down of the motor. 0 MAP signal would be pure vacuum, absolute not relative.

MAP = Manifold Absolute Pressure, by it's very definition, the sensor is an absolute sensor.

14 years tuning Speed Density systems both NA and FI, I'm 100% positive its an absolute sensor the value of which increases in value with throttle opening.

There's no doubting your log, experience or whether the MAP sensor reads in absolute scale clav.
What I am saying is that the throttle balance screen in tune ecu appears to be displaying in the gauge scale. It would appear to me that the log on the other is reading absolute values directly from the MAP
 
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