Hi,could just be a lot of condensation collected in the back section of the exhaust, due to the silly weather we've been having, I would however get a compression or leak down test just to rule out hg issues, I always let mine warm up a before driving but have recently moved house and she now lives outside, the other day I was driving half way up the road when it started chucking out a load of white smoke, found it a bit odd but it goes away as soon as it starts