Hey Pete, says here that with intercooling bigger is better http://www.airpowersystems.com.au/wrx/my01.../dr650_fmic.htm but here you write: "Be careful as bigger is not always better, we went as big as we dared (will support 650 horse power) any bigger and say goodbye to any control of the turbo pressure. Just trying to save you a lot of grief and wasted time." OzWRX