  We show that after one stabilization, a strongly irreducible Heegaard
splitting of suitably large genus of a graph manifold is isotopic to an
amalgamation along a modified version of the system of canonical tori in the
JSJ decomposition. As a corollary, two strongly irreducible Heegaard splittings
of a graph manifold of suitably large genus are isotopic after at most one
stabilization of the higher genus splitting.
