To adjust the waste gate actuator arm, pull the turbo heat shield off to access the adjustable end. Spray some penetrating oil on the lock nut to loosen it up and then unscrew that a few turns to get it away from the connector.
Then pry off the C-clip that is holding the connector on (I put a plastic bag underneath it so that if it shot off it would shoot into the bag). Once you have this done pull the connector off the post, you may have to pull the rod away from the actuator a little bit to do this.
Once you have it off you can loosen or tighten the arm depending on the direction you turn the connector. Counter clockwise will loosen it and clockwise will tighten, you want to loosen if you are having oscillations don't turn too much I don't did a half a turn. Reconnect everything and test it out.
Remember though that this may not fix the problem as these symptoms can be caused by a few different things.