The D inside the engine code means twin overhead camshaft (DOHC). This can be completed by fitting an RB25DE or RB26DETT cylinder head and or turbo to a standard RB30E/T block. The RB25DET is just not ordinarily used.Although this isn’t much an engine flaw up to This is a style and design flaw, it does have an affect on the RB30ET Within the Hold