Check your injectors
It is important to understand when the white smoke is coming. If white smoke is coming at idle or low rpm's after long motoring, it is most likely a injector problem. I had similar problem and after several trials, I was able to locate the root cause. I removed the injectors, let them re-adjusted. There is no more smoke problem since that time (2 years ago)If it is continuous white smoke, there could be other problems(injection timing, cylinder head gasket etc). Please check if it is steam or smoke? If it is steam, not smoke, there could be some problems with the cooling system.