Retuning diesel motor for more torque and hp

Transmission and rear axle...also fuel economy. Engineers will tune an engine for a specific application to achieve a balance of economy, performance, and longevity. If yours is de-tuned it's important to find out why....it could be that it's tuned to the max input rating for other parts of the drivetrain or simply to get decent fuel economy.

Not saying you shouldn't re-tune for more power, but understand first what else you are affecting.