Smokey Exhaust On Myrx350

[BlackCat]

Hello,

I picked up a second hand 2008 Lexus RX350 just before Christmas from a dealership. The vehicle passed all the proper checks and had a very well maintained log book. Since getting it I have noticed that every now and then the exhaust blows out a big puff of grey smoke. The dealership (quite a big and reputable Honda dealership) have said that it is more than likely just extra carbon in the exhaust as it was not driven very much over the last few months. Well we live just near a freeway and I have given it a really good drive but still seem to be having the problem. Sometimes it's when I am accelerating quickly and sometimes it's just when I turn on the ignition. Anyone have any ideas or have had this problem also?

Other than that the car runs beautifully and I don't think there is any lag (but I am new to a V6 so I wouldn't really have much to compare it to). It has a petrol engine not diesel.

Thanks