I don't think it is a system to "adjust" the valves in action rather a system that "activates/deactivates" valves in motion.

On the GM variable displacement engines. The fuel injector is turned off on the cylinder being deactivated and thus it just passes the air through the cylinder. I think, but don't know for sure that the valves are held open to reduce the loss of power from compressing the air in the cylinder and not having a power stroke.

Red

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2005 Titan KC SE, Helwig, True-Track, ARE MX Canopy