If it fails you just have to turn down the injector pump a bit . This will inject less fuel so there will be less "smoke". Might be a good idea to check the injectors. If you just got thte truck then it might fix itself by driving. Diesels like to get used (worked a bit) and if you don't (lots of ideling in Japan) they dont run as clean and as well. Putting some KM's on it should help with the smoke. Hope this helps.

My 84 Toyota with the 2L diesel failed last year and after I turned the injector pump down, it passed with flying colours.

1991 MITSUBISHI PAJERO EXCEED