Torque through driveline losses
Doing a ruff calculation torque at peak hp is around 92% of peak torque. 530 x .92 = 488
So say you were making peak hp at 5500 rpm. So 488 x 5500 / 5252 = 511 hp at crank. Either your losing a **** ton of power through your drivetrain or you peak way lower like 4900 rpm. Which would give you a 455 hp at crank and 80% of that is about 355 hp.
Something seems wrong.
Whats the gear ratio trans during test, tire size, torque at peak hp and rpm ?