lia2028

hi all i have a citroen c5 automatic exclusive 2.2 hdi. It is on a 06 plate with 100000 miles. The car is lovely cant fault it except one thing whenever i start if for the first time the car idles rough i was told that if i revved it up to 2500 rpm on startup that should correct it. when i rev it up i get some smoke from the exhaust. i drive off and it drives perfect no probems no dashboard lights.the car will then start with no problems at all has anyone got any suggestions