The D from the engine code means twin overhead camshaft (DOHC). This is often accomplished by fitting an RB25DE or RB26DETT cylinder head and or turbo to a normal RB30E/T block. The RB25DET is not really normally used.Although this isn’t so much an engine flaw up to it is a design and style flaw, it does influence the RB30ET inside the Holden VL