That's a fact. The brakes on the 240Z series are extremely prone to brake squeal.Yeah, there always seems to be discrepancies with shims... New pads often don't come with any, and as you discovered even Nissan pads can differ when comes to the shims fitting correctly. I just scratch my head, and proceed to do what seems feasible... I too haven't experienced break squeal for decades... I think some brake rotor/pad/designs may be more susceptible to noise than others...