A gas turbine engine steam injector includes an annular steam injection manifold aftwardly bounded by an aft manifold wall having steam injection holes disposed therethrough and located axially aft and radially inwardly of a diffuser outlet. An outer baffle wall around manifold has a curved convex surface which may generally conform to a streamline emanating from outlet. Holes may be circumferentially evenly distributed and non-uniformly sized around the aft manifold wall. Hollow struts extend between radially outer and inner bands of a diffuser and a steam supply header in steam supply communication with a fluid passage of at least one of the struts having a passage outlet open to steam cavity within cavity casing located inwardly of inner band. Openings are disposed in an aft cavity wall between cavity and the injector. Passages may be in only a non-uniformly distributed portion of the struts adjacent to each other.