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Removing the whole EGR valve from the 450 Cdi is a very complex and time-consuming procedure, which is strictly not required. You can remove and clean EGR valve in situ by removing actuator and steel valve cartridge from aluminium housing. Removing cartridge is made easier if you have in your possession a suitable tool that can turn cartridge and break it free from soot and hard deposit inside housing. Removed cartridge after cleaning using elbow grease and Mr Muscle Oven Cleaner. T25 Torx bit, 1/4" ratchet with short extension and special home made tool used to rotate and break free cartridge in housing. I have later been advised the bolts actually have 4 mm Allen heads. T25 Torx bit is therefore not the right for these small bolts and will damage the heads and make it difficult to fit the right 4 mm Allen bits. The area where the tool fits measures 28.09 mm in diameter. The slot is 5.85 mm wide. ID of tool 28.25 mm and width of tooth 5.6 mm. Tool is also guided in aluminium housing. You have to keep twisting cartridge until it moves freely and can be pulled out with pliers. I have drilled 6.5 mm radial holes in my tool so I can turn tool using a screwdriver. Exhaust inlet into valve cartridge. Exhaust outlet from valve cartridge. Exhaust flows out of the slot in above photo and out of its tip, see photo below. Close up view of seat and disc. Note that seat is serrated and burnt. It may be possible to repair by machining but cartridge can’t be easily disassembled since valve at end is TIG welded to valve stem. This valve won't seal but no major problem since I've blanked off exhaust supply at exhaust manifold. View from engine space and EGR valve aluminium housing with actuator and internals removed. Valve cartridge fits with slot facing the lower bolt hole (the most inaccessible bolt). Blanking off exhaust supply to EGR valve will ensure there is no need to open out and clean in the future. Tool is made from a brass pipe fitting. Its tooth is stainless steel and silver brazed to slot filed in pipe fitting. Tool is turned down to 39.3 mm on the OD where it is guided in aluminium housing. One can chamfer the cartridge as shown in below photo but diametrically opposite slot (12 o'clock, 6 o'clock is position of slot). Initially I chamfered 60 degrees anti clockwise from slot when viewed from actuator side but found that was no good due to my chisel interfering with car body. A sharp chisel can now be wedged into the chamfer to pry cartridge out making next time EGR clean a whole lot easier and no need for any special tools that are unavailable unless you make your own. Those lucky to have access to a metalworking lathe can chamfer the whole circumference but leave at least 0.5 mm of land.