I reckon a quaife ATB diff would help if you were doing track days, but TBH with 150bhp it cant spin the wheels up that much in a corner.

My ST170 doesnt suffer from spinning the inside wheel when applying power in a corner (with traction control off)

it does suffer from excessive understeer but not caused by power delivery, just caused from reaching max corner speed from the grip of the front tyres. Are you sure you not mixing the 2 up