Like I said before (somewhere?) assuming that there are no boost leaks or clogging problems then its all to do with injection quantity, injection duration, Start of Injection, duty cycle and boost. These will vary from remapped cars and especially cars with hybrids or big turbo's.
There are big turbo deisels with 260-70bhp with hardly no smoke...
To keep smoke levels down it comes down to maintenance of the vehicle, fuel used, additives and how its tuned software wise. As Hubsandofstinky said smoke is subjective unless you know what your looking at.