If you don’t have to the money to get a g-reddy and get it mapped have a look at http://www.megasquirt.info/ this will be much more time consuming but there systems are really good..
I think they sell a hole kit witch will be about £180 but this includes mapping and guides on building them.
http://www.megasquirt.info/ was started by a man how built his own system and put it on the net. Then other people built them and improved them and so on......now they are like a community that has really good systems.