I've yet to get the motor running to see if the ex evacs are going to work (fire up tommorow) , i'm using the Moroso ones with the 'bird beak' cut out of the tube , i thought this was 'an aid' to create more vac across the evac tube , i also heard a few others mention this , i was trying to get my head around how this 'bird beak' would help , turns out it is just a refference point when welding the evac tubes into the collectors , the instruction shows it to be flush with the outside wall thickness of the exhaust pipe to aid in correct protrusion of evac pipe into exhaust.