2004 Peugeot 407 the cars blowin grey smoke

Sorry it took so long to respond, I do have a Peugeot diesel, and I have to first congratulate you on an awesome car, we were not specific enough, I am not sure what you've done to the car or have not done, but gray smoke is a cause fuel problems, the diesel is a very reliable vehicle, at the first sign of problems you should always change your fuel filter, most likely you have water in the system restricting the fuel, there should be a bleed vale on the filter, I would also try some injector cleaner in the fuel tank, the only kind that works is the Chevron Textron, try that and get back to me and let me know
Your contributions are welcomed, Thank You