CM2350 Code 4727

[Dieseltechjon]

I have a truck right now that is doing the same thing. Repeated 4727 and I can see that the rail pressure does not drop on decel. There is no pressure in the return system and there is no air at all. I have pulled the actuator housing off the back of the block and made sure the orifice vent is not plugged or damaged. Wondering if anybody has experimented with drilling out that vent just a shade bigger. I was advised to replace it even though there are no apparent defects.