I dont see why they wouldnt. 918s are rated to .600 lift so there is still a little bit of a comfort zone there. I wouldnt try it with forced induction though. Truethfully, if I were planning on spinning my motor to 7k, I would probably go with a dual spring like the cranes or patroit golds and add some Ti retainers.

 

Why is FI so bad on springs ?

 

The boost puts positive pressure on the valves therefore causing the spring to work harder to pull it back to a closed position and keep it closed. Probablly not anything to worry about with moderate amounts of boost but when you get on up there, it is definately an issue to consider.