Description of similar event for P51 Voodoo Chile in 98.
Voodoo - 98 NCAR
Interesting link previously posted by OMGisthatJohn (and reposted here), containing an interesting aerodynamic discussion of mods made to Voodoo just prior to its event in 98, that might be insightful. I'm including a relevant quote from the article.
Reno Air Racing: Voodoo Comes Home
Weighing in at just a shade over 7200 lbs, the Voodoo sported several new modifications for 1998, including large wing fillets, a slick composite engine cowling, and a VERY smooth wing and fuselage. These mods resulted, however, in an aft c.g. condition which was most prominent at racing speeds. "With all the power that Buckwheat was carrying it kept wanting to pitch the nose up", Button explained. "It was something we were fighting all week. He kept putting more and more nose down trim into it until finally it [the elevator trim tab] got so far out into the airstream that it started to flutter. Once it went, it broke the elevator link and caused the pitch up."
Definitive photo from KOLOTV of Galloping Ghost