what is the car going to be used for? for all out performance like drag race...i'd say higher stall so you can be building boost before launch. if you going road race....i'd say closer to right at where you start to make boost so you can control the car better in turns but still have the boost/stall right there for when you roll back into the throttle with no lag.
i'm not up on turbo stuff really at all but thats what makes sense to me