My 2006 rrs tdv6 has started to occasionally belch a big puff of grey smoke when i accelerate. But when i try and get the car to do it again i cant ive tried driving real hard in town and dual carriageway but it wont smoke at all then few days later it randomly does .ive checked oil level this was spot on (has been 7 months ive had the car )same with water no loss at all .no oil in water or water in oil .any ideas please ?????..