I took it to my mechanic because of an oil leak coming from around the turbo. They said it was the turbo wearing out.it has a high pitched squeal and sounds like one of those fast and furious cars where a crackle sounds when backing off the revs.
There is some oil in the pipe, but I think that's pretty normal, the power is lacking. There is nothing too much in the way of over smoke, that's pretty normal.
It is a common story that mechanics diagnose a failing turbo, sometimes they are right, but often not.
I suggest the following:
Disconnect the pipe leaving the turbo, it will be quite oily inside. Give it a wipe with a clean cloth and look for any metal (shiny) bits, if there are any then it is time for a new turbo.
If not, then it is probably something else, quite possibly an air leak in the turbo pipework. Easily spotted as there will be a telltale oil seepage.