DUMBO - Dozens of DUMBO condo owners are suing the developer who converted the warehouse where they live into luxury lofts.The condo owners allege developer Joshua Guttman violated city building codes when converting the six-story structure. An independent investigator hired by the owners found, amongst other things, the building?s ventilation ducts don?t lead outside. Others are complaining that the building has a leaky roof, is poorly insulated and has low water pressure.Six of Guttman?s former projects have gone up in flames since 1992, including four in fires that city officials have labeled suspicious.