It is because the Z doesn't have the aftermarket support for fuel system or turbos like the Supra. The Z pistons and rods are pretty heavy duty. The crown on the stock piston is thick. But detonation under high boost and load will kill any piston. Watch out for my car when I get it done . Ask Guilly about my car and my turbos I am running. I did the work myself except for the machine work and down pipe fab. Mike