depends on budget and what power etc your after really

just to get it running the a zetec loom into the mk4 loom is good enough

to get more power and smoother running a after market management would be better

then do you have a good budget or a basic budget

if on a basic budget and can work your way around the internet for info then megasquirt is a good base to start

working onto a better management system as a when money allows