I fitted the Y-pipes about 4 weeks ago but made too many other changes at the same time to pinpoint it's actual individual effectiveness. At least the capacity to flow is greater now to assist all other and future mods. Had to modify Brendan's pipes considerably though to clear oil/water feed/return pipes and rear turbo support bracket. O2 sensor rellocation was fun as well - wires are considerably stretched now, so extending is on the cards now when I can find matching plugs. Still keen to see someone's before and after dyno graphs of the change at stock boost and ellevated boost.