The excess smoke can be deemed necessary depending on what your doing. Most the time it is excess fuel being sent through the exhaust, but the turbo on these things run off of exhaust flame. NOT the smoke. So add a little more fuel to the mix to help cool EGT on the long grades and hard pulls. Propane or nitrous can also be used but those require filling and in some states illegal. On the extreme end of the spectrum, in he truck and tractor pulling world where "pressurized" fuels are illegal it leaves you stuck with good ole #2 to make power and keep EGTs cool. When your in the throttle for about 30 seconds with your EGT staying upwards of 1600 degrees the raw black through the stacks is simply keeping things from "being to lean" in gas performance terminology, to keep from melting your $200k motor.
However, a guy can have a totally pumped up truck and if he KNOWS HOW TO DRIVE IT, will have minimal exhaust smoke. But can at will step on it and turn your headlights off in the night. Why pump them up? Fuel mileage believe it or not. I know it's crazy and probably doesn't make sense but pump up a diesel and they get better fuel mileage. If you drive sensibly. If not your mileage suffers. Basic common sense in that aspect. Hopefully that clears something's up.