This is a very broad question... You need to be more specific... Are you looking for performance mods? Fuel economy mods? Durability/reliability mods? Also, the general consensus here is before you change the factory stock configurations in any way you need to get the vehicle up to spec on maintenance items. Tires, brakes, alignment, TIMING BELT, etc...What is the best modification you have made to improve your diesel engine? Why?
Depends on what diesel you're talking about.What is the best modification you have made to improve your diesel engine? Why?