the GSR has a nice low-slope hp curve and a very flat torque curve. the P72 cams,head, and intake combo is designed for that. You'll see peaky power on the B16/17/18C5 due to the P30/whatever head, cams, and those intakes being better for building HP. the P72 intake, in particular, is restrictive to building peak hp.

I don't think 125% on a GSR is likely, but I think it makes up for that in large part due to the overall package and wide power curve, and really good driving.