Black smoke in the exhaust and in high rpm white on passat 1.9tdi

Sounds like you either have a blown head gasket and water is pushing through the cylinders and out the exhaust. Or the piston rings are worn out and you are burning oil. It would be most noticable under a load. Such as high rpms in passing gear.

Is the smoke white or black? If it's white head gasket black it oil .

the turbo your mechanic put on was 2nd hand and knackered i expect ,,,,white smoke means turbo still gone ,,,,

white smoke out of the exhaust would be a sign that it is burning coolant... if it goes away after it warms up, it could just be condensation inside the exhaust pipe. 1800 rpm is a very high idle, maybe have your IAC motor on the throttle body checked... check engine light? if so have the code read at your local auto zone.

blue is oil
White is coolant/water It will also smell kind of sweet
black is fuel

If you don't drive your car very many miles or let it sit for days/weeks at a time it is most likely condensation in the exhaust. Take her on a nice 50 mile brisk drive and see if the problem clears up. If it does think condensation if not you will need to dig further.

hmmm...This kind of problem usually is due to cam shaft/valve timing issues. Sometimes, the cam shaft is not properly positioned and is not in sync with the distributor thus the exhaust valves open early releasing unburnt fuel. This will cause the engine to definitely run bad.
I suggest that you try to adjust your engine's timing first (cam and distributor) and then see the results. Also, remember that there is a limit to the rpm that an engine must do- about 6,000rpm is enough for high or max hp. Another information, a camshaft will only work best at a given rpm range so if you run your engine too low or too high, the engine will not work properly. In fact, there are special cam shafts for engines intended to run at high rpm while sacrificing lower rpm levels (the engine runs grumpy at low rpm levels).
Worst case, however, is that white smoke sometimes indicates that oil enters your combustion chamber, this will cost an expensive rebuild if such is the fact.

Sounds like blown head gasket soery

This sounds like you have a seal that is failing under the stress of high engine and turbo rotor rpm's, the white smoke is oil burning, either in the exhaust stream or it's oil getting into the intake stream and being burned with the fuel..
You can remove the turbo yourself but you may not be able to locate the issue.
I would advise that you take the vehicle into a turbocharger specialist..

Does the smoke occur all the time? If it is present just after start up and then goes away, it could be no problem at all. There is always some condensation in the exhaust at start up. It is more noticeable in cold weather.

However, if it is there constantly, and you are losing coolant, it could mean there is a headgasket problem. Watch your coolant level and watch your temperature gauge. If the coolant starts disappearing, and the car starts overheating, stop it immediately and get it to an auto repair shop. Driving a car with a bad headgasket can cause major engine damage.

White smoke from exhaust indicates burning coolant. Blue smoke from the exhaust indicates burning oil. In replacing the valve cover gasket for an oil leak, some smoke from residual oil is normal but it would be excess oil burning off on the manifold from the engine compartment, not the exhaust. Hope this helps with your question.
Greg