A turbocharger, comprising: a turbocharger housing; a two-sided compressor wheel; and a rotor being mounted for axial rotation within the turbocharger housing, the rotor including a shaft extending axially between a turbine wheel and the two-sided compressor wheel; the two-sided compressor wheel further comprising: a first set of compressor blades having a first set of blade parameters consisting of a first wheel trim and a first annulus area; a second set of compressor blades having a second set of blade parameters consisting of a second wheel trim and a second annulus area; wherein the values of the first set of blade parameters are not all identical to the values of the second set of blade parameters; wherein the housing defines a diffuser for the two-sided compressor wheel, the diffuser including a first portion surrounding the first set of compressor blades of the two-sided compressor wheel, and the diffuser including a second portion surrounding the second set of compressor blades of the two-sided compressor wheel; the turbocharger being characterized in that: the diffuser has a first annulus area ratio DE 1 for the portion of the diffuser surrounding the first set of compressor blades, and a second annulus area ratio DE 2 for the portion of the diffuser surrounding the second set of compressor blades; wherein for a set of blades: given D i2 being the diameter of the hub edge of the path of the blades at their inducers, B i2 being the axial width of the set of blades at their respective exducers, D i3 being the diameter of a downstream end of the diffuser, B i3 being the final axial width of the side of the diffuser, e i being the axial distance between the shroud edges of the blades and the shroud at the exducer, and w being the width of the backplate at the exducer, the annulus area ratio DE i, is defined by the formula; DE i = D i 3 B i 3 D i 2 B i 2 + e i + 1 2 w and wherein the first annulus area ratio DE 1 is not identical to the second annulus area ratio DE 2. a turbocharger housing; a two-sided compressor wheel; and a rotor being mounted for axial rotation within the turbocharger housing, the rotor including a shaft extending axially between a turbine wheel and the two-sided compressor wheel; the two-sided compressor wheel further comprising: a first set of compressor blades having a first set of blade parameters consisting of a first wheel trim and a first annulus area; a second set of compressor blades having a second set of blade parameters consisting of a second wheel trim and a second annulus area; a first set of compressor blades having a first set of blade parameters consisting of a first wheel trim and a first annulus area; a second set of compressor blades having a second set of blade parameters consisting of a second wheel trim and a second annulus area; wherein the values of the first set of blade parameters are not all identical to the values of the second set of blade parameters; wherein the housing defines a diffuser for the two-sided compressor wheel, the diffuser including a first portion surrounding the first set of compressor blades of the two-sided compressor wheel, and the diffuser including a second portion surrounding the second set of compressor blades of the two-sided compressor wheel; the turbocharger being characterized in that: the diffuser has a first annulus area ratio DE 1 for the portion of the diffuser surrounding the first set of compressor blades, and a second annulus area ratio DE 2 for the portion of the diffuser surrounding the second set of compressor blades; wherein for a set of blades: given D i2 being the diameter of the hub edge of the path of the blades at their inducers, B i2 being the axial width of the set of blades at their respective exducers, D i3 being the diameter of a downstream end of the diffuser, B i3 being the final axial width of the side of the diffuser, e i being the axial distance between the shroud edges of the blades and the shroud at the exducer, and w being the width of the backplate at the exducer, given D i2 being the diameter of the hub edge of the path of the blades at their inducers, B i2 being the axial width of the set of blades at their respective exducers, D i3 being the diameter of a downstream end of the diffuser, B i3 being the final axial width of the side of the diffuser, e i being the axial distance between the shroud edges of the blades and the shroud at the exducer, and w being the width of the backplate at the exducer, the annulus area ratio DE i, is defined by the formula; DE i = D i 3 B i 3 D i 2 B i 2 + e i + 1 2 w and wherein the first annulus area ratio DE 1 is not identical to the second annulus area ratio DE 2.