more smoke=safer engine. If you have less smoke you are running leaner and the engine runs hotter. The hotter the engine gets the more likely it is to start damaging itself. You want to find the point where the engine dose not get to hot but gives you the best preformance. If both are running the same truck and you are just has fast has him or maybe just a little slower then he is running to lean and damaging his engine. If he is running way faster you are prolly running to lean. Again that only applies if it is same truck and engine.