Let $\omega$ be a nonreal root of $x^3 = 1.$  Compute
\[(1 - \omega + \omega^2)^4 + (1 + \omega - \omega^2)^4.\]
We know that $\omega^3 - 1 = 0,$ which factors as $(\omega - 1)(\omega^2 + \omega + 1) = 0.$  Since $\omega$ is not real, $\omega^2 + \omega + 1 = 0.$

Then
\[(1 - \omega + \omega^2)^4 + (1 + \omega - \omega^2)^4 = (-2 \omega)^4 + (-2 \omega^2)^4 = 16 \omega^4 + 16 \omega^8.\]Since $\omega^3 = 1,$ this reduces to $16 \omega + 16 \omega^2 = 16(\omega^2 + \omega) = \boxed{-16}.$