I would think it would be better to trigger meth based on MAP pressure than RPM, unless that's just a window switch and it's still based on MAP in addition.

Just to follow up on this, I had the Aquamist HFS-3 installed last week and spent yesterday with my tuner. It's working great for AITs, it was 85 degrees yesterday and when the meth was running the max temp was around 100 degrees. My plan to not tune for it didn't work with this system because with all the meth it pumps it made the car way to rich. We ended up doing a second set of maps so I can run it with or without the meth so I'm happy with the kit.