s40 t4 (how do I tell if its blown)

Coming into work today noticed then when I accelerated that smoke was coming out of the back. mate who was following me said that it looked blue, but I thought it was white. Checked the oil level while in work and the oil and water, no problems appear to be evident i.e no water in the oil and no oil in the water. Engine runs ok and is smooth so could the problem be the turbo blown car has covered 67000 miles.
whats the life of the turbos??

If its has blown how much are replacment units???? iam in the uk.

I'm not a complete expert on the matter of turbo cars, but I know that on fairly unrestricted exhaust systems it is very common to get smoke or flames on the upchange or overrun. My normally-aspirated car does this (with no catalyst). If you accelerate hard to say 4000rpm and then back off, feathering the pedal, it is at this point that unburnt fuel ignites and makes its way down the exhaust tube - perfectly normal in my book.

I would expect that the odd puff of black smoke was fairly normal if you really burried the pedal in the wilton and gave it the Full George when your mate was following you. I have chased many standard turbo cars and been pelted with plooms of black smoke (Fiat Coupe Turbo in particular). Blue smoke is an entirely different matter though.

Many turbo cars benefit from a minute or two of idling before and after use of the car - to allow the oil to circulate around the turbo bearings and hence prolong the life of the turbo itself. This is probably less applicable to your car than to say, a Renault 5 GT Turbo, though I would recommend it if you had just given the car a proper thrashing and were about to turn the engine off.