I wanted to compression test the engine to make sure that the valve seals, head and injectors were seated correctly. The BMW service manual states to do this by removing the glow plugs - which seemed like a much better idea than having to remove the injectors. I soaked the glow plugs in PlusGas for a day or so and then removed the glow plugs. One snapped and had to be drilled and pulled out, but this was eventually completed successfully.