Bad seals in the turbo could cause it.
I think the restrictor will help, but you need to find out if the turbo is leaking. Any signs of oil on the outside of the turbo? Then check the piping (both sides) for oil. If you have oil, bad news for the turbo.
To give you a little peace of mind. . .run the car (not too hard though, just normal), then open the oil fill. If a bunch of smoke rolls out, you could have bigger issues, if just a little or none comes out, then it is probably the turbo. Sorry to hear of the problems, I feel your pain.