Mountainman, can you snap a quick video and put it on YouTube? That's more helpful that explaining in words.
Injector knock usually sounds like you get a hammer and smack a solid thick piece of metal, it can vary in intensity and loudness depending on how bad it is. It is caused by impartial burning (you get more diesel through than you should) or an obturated nozzle(s). So instead of diesel being pulverized you get some sort of stream. If gmctd sees this post, he may be able to add more info to it as he's pretty god with this kind of explanations.
This link for the Vw alh engine has injector knocks and few "misses".
http://m.youtube.com/watch?v=2uRbaTdg8AEFunny that engine is a bit shy of 500k...
In my case, I get a few "misses", but only at cold and very intermittent. Once the engine warms up a bit, runs perfectly fine. Stage one of an injector knock is usually at cold and at idle/light throttle. Stage 2+ is when it knocks all the time, this can cause very high Egt temps and you may put a hole in the piston, but you shouldn't worry about this yet.
Please post a video with the sound, will help in identifying the noise. As papaindigo said, some power service or an injector cleaner may help if your nozzles are dirty, otherwise I doubt it will do much.
Another way to identify the noise is a mechanical stethoscope and listen to each injector, you'll hear the one(s) knocking.