A method of manufacturing a compressor housing comprising: arranging a core with a die so as to define a mould cavity between a surface of the core and a surface of the die, the mould cavity having the shape of a compressor housing; providing a molten metal within the mould cavity and solidifying the molten metal to form a compressor housing; the compressor housing having a longitudinal axis and being for receipt of an impeller wheel, mounted for rotation about an axis; the compressor housing comprising an annular diffuser first wall member having a surface for defining, with an opposed surface of an annular diffuser second wall member, an annular diffuser passage; the surface of the first wall member of the diffuser extending radially outwardly from an annular inlet end to an annular outlet end and having an annular outlet section extending radially inwardly from the outlet end; the compressor housing further comprising an annular outlet volute first wall member having a surface for defining, with a surface of an annular outlet volute second wall member, an annular outlet volute passage; the surface of the annular outlet volute first wall member defining a volute channel that extends, along a circumferentially extending volute channel axis, about the compressor housing longitudinal axis; the surface of the annular outlet volute first wall member having an annular inlet end, provided at the outlet end of the surface of the first wall member of the diffuser, the surface of the annular outlet volute first wall member having an annular first section that extends axially outboard from the annular inlet end; the compressor housing being formed such that for at least one circumferential position about the compressor housing longitudinal axis, a first external angle is subtended between the outlet section of the surface of the diffuser first wall member and the first section of the surface of the outlet volute first wall member; the outlet volute first wall member being formed with an opening; wherein after the compressor housing has been formed in the mould cavity, the core is removed from the volute channel; said method being characterized in that once the core has been removed from the volute channel, a cut is applied, through the opening, to the first section of the surface of the outlet volute first wall member, at the at least one circumferential position, to produce a cut section such that a second external angle is subtended between the cut section and the outlet section of the surface of the diffuser first wall member, at said at least one circumferential position, that is greater than the first external angle. arranging a core with a die so as to define a mould cavity between a surface of the core and a surface of the die, the mould cavity having the shape of a compressor housing; providing a molten metal within the mould cavity and solidifying the molten metal to form a compressor housing; the compressor housing having a longitudinal axis and being for receipt of an impeller wheel, mounted for rotation about an axis; the compressor housing comprising an annular diffuser first wall member having a surface for defining, with an opposed surface of an annular diffuser second wall member, an annular diffuser passage; the surface of the first wall member of the diffuser extending radially outwardly from an annular inlet end to an annular outlet end and having an annular outlet section extending radially inwardly from the outlet end; the compressor housing further comprising an annular outlet volute first wall member having a surface for defining, with a surface of an annular outlet volute second wall member, an annular outlet volute passage; the surface of the annular outlet volute first wall member defining a volute channel that extends, along a circumferentially extending volute channel axis, about the compressor housing longitudinal axis; the surface of the annular outlet volute first wall member having an annular inlet end, provided at the outlet end of the surface of the first wall member of the diffuser, the surface of the annular outlet volute first wall member having an annular first section that extends axially outboard from the annular inlet end; the compressor housing being formed such that for at least one circumferential position about the compressor housing longitudinal axis, a first external angle is subtended between the outlet section of the surface of the diffuser first wall member and the first section of the surface of the outlet volute first wall member; the outlet volute first wall member being formed with an opening; wherein after the compressor housing has been formed in the mould cavity, the core is removed from the volute channel; said method being characterized in that once the core has been removed from the volute channel, a cut is applied, through the opening, to the first section of the surface of the outlet volute first wall member, at the at least one circumferential position, to produce a cut section such that a second external angle is subtended between the cut section and the outlet section of the surface of the diffuser first wall member, at said at least one circumferential position, that is greater than the first external angle.