Like to find a service manual with the vacuum values for normally aspirated B230 with LH-Jetronic 2.4.

Someone here may have a service manual for 240 with these values.

Vacuum drops as you press the gas pedal. Yes, a wide open throttle body when you floor causes the vacuum in the intake port (injection) manifold. The vacuum controlled control pressure regulator respo0nmds to the loss of vacuum with wide open TB by allow more fuel to pass through the batch injection.

As you have the M47 II, do NOT hold the clutch down at long stops or RxR crossing. Use the clutch to change in to and out of a gear. Or else a bunch of stuff can wear in the clutch kit, throw out bearing. Also, when last did you replace the gearbox fluid. See the overfill method in the FAQ for manual transmission. Use Volvo OEM, Amsoil, and Redline as these site recommend for replacement fluid.

The engine vacuum drive HVAC flap under the dash can leak. Ends of rubber lines detach. In the passenger footwell under the center console side kick panel, as you know, or must know. This connection can leak, as any other. You'll have to inspect all concerns vacuum. The gauge reads the vacuum in the intake manifold downstream of the TB. Vacuum at idle and TB closed with now leaks I read as optimally 20 inches of mercury (Hg) as vacuum or negative pressure.

http://forums.turbobricks.com/showthread.php?t=233878

This forum is replete with article on the reason why you post. Try the search or use google / bing and target the brickboard.com, domain.

Find vacuum piping diagrams onsite like the Volvo Parts Webstore, Oz Volvo Technical Archives, and http://www.v8volvo.se/mekartips/volvo/. Search here for other resources.

After a month, I expect someone to help you.

All I can do is:

https://www.240turbo.com/volvovacuumdiagrams.html

Hope that hepkats.
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Beh.