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I'm looking for a link to the actual report to see if the "environmentally friendly" reformulation of the insulating foam is mentioned.

I'm sorry to report that the following small paragraph in Chapter 3 (1.6Mb .pdf) is the only mention of the change in the foam. (I hope some FReeper can prove me wrong on this, but I can't find any other mention at all).

Throughout the history of the External Tank, factors unrelated to the insulation process have caused foam chemistry changes (Environmental Protection Agency regulations and material availability, for example). The most recent changes resulted from modifications to governmental regulations of chlorofluorocarbons.
...The foam types changed on External Tanks built after External Tank 93, which was used on STS-107, but these changes are beyond the scope of this section.

That's it? Or is there another "section"?

There is an informative chart on Page 127 of the report that shows "the number of dings greater than one inch in diameter on the lower surface of the Orbiter after each mission". An eyball review of this chart shows the number of dings rising dramatcally starting with flight 86, which was in 1997.

From page 129:

"The foam loss problem on STS-87 was described as “pop-corning” because of the numerous popcorn-size foam par-ticles that came off the thrust panels. Popcorning has always occurred, but it began earlier than usual in the launch of STS-87. The cause of the earlier-than-normal popcorning (but not the fundamental cause of popcorning) was traced back to a change in foam-blowing agents that caused pres-sure buildups and stress concentrations within the foam. In an effort to reduce its use of chlorofluorocarbons (CFCs), NASA had switched from a CFC-11 (chlorofluorocarbon) blowing agent to an HCFC-141b blowing agent beginning with External Tank-85, which was assigned to STS-84. (The change in blowing agent affected only mechanically applied foam. Foam that is hand sprayed, such as on the bipod ramp, is still applied using CFC-11.)"

I was unable to download the document until now. This morning the internet server must have been jammed with traffic.

page 11 and 12 state that:
"the direct, physical action that initiated the chain of events leading to the loss of Columbia and her crew was the foam strike during ascent."

The debris strike is discussed on page 34. CAIB apparently noted THREE pieces of debris. We had extensively conjectured about the other impacts since CAIB was not publicly commenting upon the other pieces. The CAIB report states that "one large piece and at least two smaller pieces of insulating foam separated from teh ET left bipod ramp area..."

In post 225, I estimated size at 50 cm by 5 cm going 340 mph.

NASA CAIB estimated 21-27 inches (53 - 68 cm) in length, 12-18 inches (30 to 45 cm) in width, moving at 416-573 mph.

So, it looks like I wasn't too far off the mark in my FR estimate.