Turbo ECM cm870

[Chamberpains]

Its called the turbo actuator control module. You should hear the turbo spooling completely different. It will change pitch according to what the engine needs to meet your demands. Your stage 3 jakes will be A LOT more responsive.
Its good to see you went with a new Holset module. Stay away from reman Ebay ones. They will give you more trouble than the $200 savings is worth. Very shotty workmanship.

Is this for your Volvo?
How did you troubleshoot it?
If you have Insite go ECM diagnostic Tests and test the actuator air supply. Make sure there are no leaks anywhere in the piping and actuator itself. Stand next to the actuator and toggle it on off a couple time. Make sure you have no air leaking out around the armature. All air in the system should be purging out of the bottom of the control module.
Also be very careful with your teflon tape. Cummins install instructions recommend that you don't use it on any part of the air system for fear of unknowingly getting some inside the system. This system is very finicky and any kind of obstruction, including pinches, buldges, kinks or very minute leaks will throw it out of whack.

The ECM will adjust to leaks by pushing more actuator command percentage. But a lot of times it will over compensate, especially if the leak stops with the build in pressure. I found this out on mine when a leak on the actuator at around 30-50% command range and no where else. I would get violent boost spikes as the leak sealed passed the 50% range on the actuator and the ECM couldn't compensate fast enough.
1 last thing to check is make sure you have 90 psi supply to the module. I think the last update of the module comes with a pressure regulator built inside so if you have more than 90 psi to it, it should be fine.
My International runs the supply thru a 90 psi reducer\regulator attached to the brake treadle valve.