A method can include applying a force to a control arm operatively coupled to a shaft; transmitting at least a portion of the force from the shaft, via an arm, to a plug positioned with respect to a wastegate seat of a turbine housing; maintaining an isostatic condition for relative positions of the shaft, the arm and the plug wherein contact exists between the plug and the wastegate seat; and in the isostatic condition, fixing the relative positions of the shaft, the arm and the plug via welding.