Hatterasguy,

Your engine is running roughly after a cold start?
HTH gave you a good explenation. If there is really an injector problem you should see smoke with a warmed up engine too.
Are you shure ALL your glow plugs are working? If not, you'll have smoke after a cold start that will disappear together with a clattering sound after say 15-60 seconds, depending of ambiant outside temperature. Knowing your usual mpg is a good indication too.

Danny