Best modification?
 

Hello - I am working with an automotive manufacturer and would like to learn more about diesel engines. What is the best modification you have made to improve your diesel engine? Why?

thanks!

Better fuel filtration, help save your injectors.
Gauges to monitor your motor.

Filtration- injector life.
Exhaust- lower egt's
intake- cooler air, and more of it.
I went overboard though...intake, exhaust, injectors, cam, fuel preporator, programmer, giant turbo. love 'em all.