Regarding the redline diesel additive:
I am having a similar issue, with lots of rattling/knocking/clattering while cold, especially during acceleration. I've used "Diesel Doctor" in the past (putting it directly in the fuel line, not in the tank), which REALLY makes the engine purr like a kitty... for a week or so. After two weeks it's the same as it was before.
Valve adjustment seemed to help a little bit, but as the weather is getting colder it seems to be getting worse. Since the additive helped so much, I'm guessing it's the injectors... any other thoughts?