WI based on Fuel delivery or maniflod pressure?

[FastAOD]

Ive noticed with a few progressive controllers out that base the water delivery on injector cyle/fuel delivery. This seems like a great idea. But i am wondering if injecting the water based on maniflod pressure would be more ideal?

I would think being able to inject water, progressivly, based on maniflod pressure would be the way to go, since the need for water is directly based on additional cylinder pressure?

Just wondering what peoples general opinions are on this.....