Hi Steve,
There are different options to go but as campbellju said, best to give us an idea of what you want your car to be as that will help us give you a proper spec up.
Here is my build which should give you an idea -
http://www.gtiroc.com/index.php?threads/mad4its-gtir-602bhp.56962/
A couple of pointers -
Rods not essential at 500bhp but recommended
Use standard head bolts / studs, do not use ARP ones, they tend to lift the head
I have a single throttle body on mine, to be honest, I cant remember where it came from or what difference it makes.
ECU makes a lot of difference. Nistune and Apexi are the most common ones and will do 500bhp. After that, I would recommend Syvecs and speak to Ed at Fusion Motorsport as he is the best gtir mapper in the UK and beyond. If you dont get hold of him, keep ringing, he dont like answering the phone lol.