Blue and white smoking on idle only

Hello I was wondering if anyone can help me, I have an octavia 2 2.0tdi bmm engine I have recently replaced the exhaust manifold gasket around 2 weeks ago and since then when the vehicle is hot and stood in traffic for approximately 2 minutes there is quite abit of white and blue smoke when you set off it clears and it's OK. I have checked the oil level,  all OK, checked coolant all OK checked for any oil leaks all OK I am really stumped and was wondering if anyone can point me in the right direction. 

Many thanks