More than this I didn't find:

Stage1: STD EXHAUST HOUSING, LARGER COMPRESSOR WHEEL, UPRATED THRUST BEARING (NOT 360 deg) -31 ACTUATOR

Stage2: STD EXHAUST HOUSING, LARGER COMPRESSOR WHEEL, 360 deg THRUST BEARING, -31 ACTUATOR

Stage3: LARGER EXHAUST HOUSING, LARGER COMPRESSOR WHEEL, 360 deg THRUST BEARING, -31 ACTUATOR