BMW M2/M3/M4 S55 Big Turbo UpgradeCarBahn turbocharger upgrade system for the F series M2C, M3, M4 are new not rebuilt units. They come with larger compressor wheel and housings, Larger turbine wheel and housing and a new high performance exhaust manifold casting. The turbo upgrade makes the turbocharger more efficient at higher volumes. This reduces charge air temperature at high RPM. The reduction in temperature means we can run more boost safely. This superior design has more flow