The nut attaching the EGR tube to the valve is tight on mine although it has come lose in the past. I have not thrown any codes but I still seem to lose boost particulary when the engine is completely warmed up and I have driven it while. It seems to occur when it is hot and I let it sit for awhile. That is why I think it has something to do with heat soak throughout the S/C and engine components. I have checked for any vacuum leaks, none found, the belt is not slipping and can find no other cause for the condition. Any advise would help.