Normally there is only one kind of conversion for diesel vehicles, and most of the time, with latest diesel vehicles, most modifications are electronic. We rarely change the exhaust systems on diesel vehicles. The advantage of diesel engines is that you have better control of where you want the engine to perform at its best, unlike petrol engines. The disadvantage of diesel engines is that you are restricted with the combustion temperature of the engine, it CANNOT run to hot, especially in a country like South Africa where the ambient temperature can get very hot! Diesel engines do NOT like HIGH RPM!!!
In order to get more power and torque out of your diesel vehicle it is necessary to inject more fuel into the engine at the right time, to be able to do that we have to get more air into the engine, otherwise it will run too rich causing high combustion temperatures. Luckily most of the common rail diesel engines are manufactured with turbo chargers, so by raising the boost we manage to get more air into the engine, allowing us to add fuel, resulting in higher torque and power output. When your vehicle produces more power, it will maintain your CRUISING speed with less effort, resulting in improved fuel economy.