Field strip the pistol, then drift the pins out of the frame and pull the receiver out..pay attention to the slide catch as it is laying against the receiver and frame with a spring behind it.
Once you have the receiver out look at the right side of the receiver and you should see two phillips head stove bolts, they sandwich the barrel in place.
If the bolts are loose it will allow the barrel to wobble, put some loc-tite on them and retorque them down. This is the usual culprit to accuracy issues with that pistol.
It is possible that the additional weight of the suppressor is causing the barrel to shift when it is installed.