Well there was one tornado in 2005 that was rated F4 and two were rated F4 in 2006. I believe they were Madisonville, KY, Monroe City, MO, and Crosstown, MO. That Westminister, TX in above photos was definitely stronger then the three I mentioned. There was also a couple other tornadoes in April of 2006 that should have been rated F4 as well. MEG did those surveys.
Supposedly MKX considered an F4 rating for the Stoughton, WI tornado of August 18, 2005 (which just missed the house where I was living at the time/where my parents still live). They settled on high-end F3 which seemed to be the standard of '05-'06. In my amateur opinion, that was an accurate rating though. The well-built houses in the worst damaged areas generally had textbook F3 damage (only some first-floor interior walls left standing). Houses that were swept away were poorly anchored "sliders." Vehicles were moved/flipped but not hurled long distances and mangled beyond recognition.