as gracie says

Is the oil return suitable?? ie fez t2 always smoke but it isnt the turbo its the shit return,oil cant escape quick enough, also have you removed any boxes out of the exhaust?? also common thing ppl think turbos give up when actually is less backpressure for the rear oil seal. In general if you accelerate there is no smoke but on overun and throttle after it will smoke (especially throttle after overun) also sat at lights and your engulfed in smoke from behind, its you