A wealthy Wall Streeter has roiled Carnegie Hill with plans to turn three landmarked homes into one. Dr. Mitchell Blutt wants to combine the three Romanesque Revival, four-story town houses into one 17,000-square-foot home. He already owned a home on East 90th Street, between Park and Madison Avenues, and bought the two townhouses east. Preservationists say the plan is out of character for the neighborhood and don’t like a proposed three-story rear-yard addition and an additional fifth floor. Blutt was an original members of Chemical Venture Partners, a Chemical Bank affiliate, and later became an executive partner of J.P. Morgan Partners.