Kidd_Stylez

I have two turbo related questions, 1) why does it seem that a 4 bolt housing is preferred to a 5 bolt and what is the difference (besides # of bolts)? 2) What is the upgrade done to a turbo that has a T-60 after it? Sorry for my ignorance and i have already tried the search function and got nothing. Thanks for any info that might help me.