From what little I know, the filter doesnt make a difference as the throttle is drive by wire, so it only needs to open the throttle enough to get enough air in to satisfy its own demand. In a normal car, the throttle opens relative to the throttle pedal, so at WOT a less restrictive filter will let more air in. However, the Zed being a clever bugger say, oh no, I have as much air as I need so I will only open the throttle 90% rather than 100% Thats how I see it working