The Professional Products Cyclone competes with the Edelbrock Performer. The Professional Products Typhoon competes with the Performer RPM and the Pro Products Crosswind is the equivalent of the Air Gap.
If you study the design of the Performer RPM and the Air Gap you will see that the design of the plenum and the runners are nearly identical. The only difference is the Air Gap has an open space under the plenum and runners.
This is also true for the Professional Products Typhoon and Crosswind. The core used in the casting process, which is what is used to form the internal open spaces of the manifold (plenum and runners) is identical between these two manifolds.
So typically the only performance difference that you will get is the open area under the plenum helps keep heat transferring from the engine to the manifold and the fact that outside air passes through this area also promotes a cooler air intake charge. I have never seen any direct comparison dyno tests but I would have to believe the the actual gain is fairly small. Probably in the range of 3 or 4 HP.