They have always been regarded as a quick and 'cheap' route to more power for the later L series engines. I put 'cheap' in inverted commas because they also result in significantly increased fuel consumption - the extra power has to come from somewhere, but the SDI injectors when used in the later engines do seem to produce more soot and smoke (excessive smoke = inefficient/incomplete combustion), so not all that extra fuel is producing extra power. MPG with the SDI mod seems to be not much better than the mpg for the petrol K series from the mpg figures that the diesel fans on here have posted in the past.
You will possibly find more information in threads within the diesel section of the 'Ask the Gurus' part of the forum.
You will possibly find more information in threads within the diesel section of the 'Ask the Gurus' part of the forum.