Turbo blew up lots of smoke from under bonnet and out of the back.will this have ruined the engine?

The smoke is due to the leaking oil. there is a common problem where the oil hose that feeds the turbo leaks, and drips on exhaust. Open bonnet on cold engine and clean the rear part using degreaser of sprayer, start up the engine and let it idle while checking the rear . for better results i usually pull the car up on a white sheet of cardboard or paper so i can see where it drips or splutters the oil on top the paper. Turn off car about 10 minutes in and check under the car. the area where you see oil will tell you where to investigate further. Another common VW problem is the tappit cover gaskit that leaks from time to time. Remove plastic engine cover and have a look

Hi I'm Peter, your gasket from either your oil supply or return on the turbo have come loose and is spewing oil or you sucked in a seal on your turbo.

it could have engine dammage or just that the exhaust is full of engine oil from old turbo blowing up and its burning off
is the engine oil going down? if so motor damage

check your turbo again. also check whether the waste gate valve is working by testing it with vacuum tester.Or check if any flex hose on turbo or inlet manifold has not cracked or sheared and cause a leak and that is why you might have low power with lots of smoke.

sounds about right for what i think it is ,now remove the EGR valve and make a gasket from a coca cola can and do not cut the middle out ,so it blocks it off completely then try it as i am almost positive this is your problem .

A new turbo charger is about $340, but you can buy the bearings and seals and rebuilt if yourself for about $100
http://turbosandparts.com/
It is not hard, and it does not take long to do.

I normally do not bother with synthetic, but with a turbo charger, it might be worth it. What really seems to ruin turbo chargers the most is not letting them cool off before parking.
Once you turn off the engine, there is no longer any cooling, so the build up heat will burn up the oil and seals.
Run the engine for at least 5 minutes below turbo levels, before shutting down the engine.

take the inter cooler pipe of turbo and try to move the fan or bolt inside the turbo, if you can then theres a problem with the bearing probably oil starvation parts of the fan will have been sucked through the engine so this could cause the smoke problem if the plastic is stuck in the exhaust valve check all oil lines and air lines, try getting some one to hold rag over exhaust pipe and look in engine bay if you can see smoke/exhaust gases coming from turbo unit then theres a leak somewhere,
its a complicated problem and without being there i cant really help anymore than that, sorry jezza

White smoke from exhaust = water into the cylinders, when this happens it usually means head gasket gone or starting to go.
Check the water level, and take the car to the garage for a check up , if it is the head gasket, as I think, you risk to blow the engine at any time.

either engine has too much oil or turbo bearings gone and it was running on the engine oil being sucked through the turbo.frightening experience and good job you had mind to stall engine before it blew itself up