Another perhaps significant thing to consider:

After searching for matches to Tut/AmIII/KV55 samples at ySearch.org http://www.ysearch.org/haplosearch_view.asp?haplo=R1b1b2&viewuid=ER7RQ&p=0

I saw that the 18th Dynasty samples, when compared to matching R1b's (matching 10-17 y-STR markers w/genetic distance of 6) I noted a key dissimilarity:

Y-STR markers 426 and 388 are absent in the mummies, but present in the ethnic European. Y-STR 426 and 388 are also absent in my I1 makeup.

I don't know enough about the science to speculate, but if those markers are missing in African-descended people with yEuro haplotypes it could perhaps warrant investigation.

When it comes to identifying the genetic makeup of Egyptian mummies, populations possessing those markers should be excluded from consideration if other mummies show the same trend.