BIG-BOY

Okay right now I'm having a hard time trying to figure out which way to go here hiboost now offer's in every kit a T03/T04e turbo and tial waste gate but for the steep price of $4,000 damm that's alot of money....but I can afford it and everything that will come in my way. And then there is a custom kit which everybody tell's me to do and I will save lot's of $$$... if I were to go custom I know one of my 100 promblem's to solve will be the damm MAP sensor,tuning etc...........Can anyone tell me why is there a need for a stand alone ecu such as haltech,e-manage etc.......for only to boost at 5-6psi? and what about timing do I retard the crank sensor manually at the block or does the stand alone ecu do it? why not a AFC II ??