An assembly comprising: a wastegate that comprises a shaft, a wastegate arm and a plug portion positionable in a closed operational state and in open operational states; and a turbine housing component that comprises a bore for receipt of the shaft, the shaft rotatable in the bore to position the wastegate in the closed operational state an in the open operational states, wall and floor surfaces (946, 948) that define an exhaust chamber, a passage to the exhaust chamber defined by a surface of a wall, the passage extending along an axis to a wastegate opening, a wastegate seat disposed a radial distance about the wastegate opening to seat a surface of the plug portion in the closed operational state of the wastegate, and a wall that rises above and axially away from the wastegate seat into the exhaust chamber to establish a relationship for exhaust flow from the passage via the wastegate opening to the exhaust chamber with respect to the open operational states of the wastegate wherein the wall comprises a minimum axial height from the wastegate seat that rises to a maximum axial height from the wastegate seat over an azimuthal angle about the axis and wherein the maximum axial height corresponds approximately to a position on the plug portion of the wastegate that experiences the greatest axial displacement for open operational states of the wastegate. a wastegate that comprises a shaft, a wastegate arm and a plug portion positionable in a closed operational state and in open operational states; and a turbine housing component that comprises a bore for receipt of the shaft, the shaft rotatable in the bore to position the wastegate in the closed operational state an in the open operational states, wall and floor surfaces (946, 948) that define an exhaust chamber, a passage to the exhaust chamber defined by a surface of a wall, the passage extending along an axis to a wastegate opening, a wastegate seat disposed a radial distance about the wastegate opening to seat a surface of the plug portion in the closed operational state of the wastegate, and a wall that rises above and axially away from the wastegate seat into the exhaust chamber to establish a relationship for exhaust flow from the passage via the wastegate opening to the exhaust chamber with respect to the open operational states of the wastegate wherein the wall comprises a minimum axial height from the wastegate seat that rises to a maximum axial height from the wastegate seat over an azimuthal angle about the axis and wherein the maximum axial height corresponds approximately to a position on the plug portion of the wastegate that experiences the greatest axial displacement for open operational states of the wastegate. a bore for receipt of the shaft, the shaft rotatable in the bore to position the wastegate in the closed operational state an in the open operational states, wall and floor surfaces (946, 948) that define an exhaust chamber, a passage to the exhaust chamber defined by a surface of a wall, the passage extending along an axis to a wastegate opening, a wastegate seat disposed a radial distance about the wastegate opening to seat a surface of the plug portion in the closed operational state of the wastegate, and a wall that rises above and axially away from the wastegate seat into the exhaust chamber to establish a relationship for exhaust flow from the passage via the wastegate opening to the exhaust chamber with respect to the open operational states of the wastegate wherein the wall comprises a minimum axial height from the wastegate seat that rises to a maximum axial height from the wastegate seat over an azimuthal angle about the axis and wherein the maximum axial height corresponds approximately to a position on the plug portion of the wastegate that experiences the greatest axial displacement for open operational states of the wastegate.