There's 3 things you can spray ON an intercooler. You can use water. You can use CO2 which is a lot more common. You CAN use Nirous oxide (kinduv stupid, though).

Usually when people have the intercooler sprayer on their nitrous kit, it's just hooked up to the purge. This is so that the wasted precious giggle juice that was paid for by the lb gets used for SOMETHING constructive. When you see someone's car doing this, it's more likely that they're using CO2 because it's much less expensive, twice as effective, and can be used in conjunction WITH N2O.

Marty, a guy I know with a heavily tuned Galant VR-4 (AWD 4-door that can pull the front wheels when it launches) reported nearly the same sort of gains with the CO2 sprayer. He achieved more than 100% efficiency with that combo, meaning the charge air... though more dense... was even colder than the ambient air temperature. BUT his intercooler core is over 30" long, 12" tall and 3.75" thick. It was already very efficient. I've heard FWD reports that it's the difference between traction in 3rd gear, and no-traction torque-steering all the way through 3rd gear. I never trust anyone else's butt dyno, but it wouldn't surprise me one bit if they have a large enough intercooler.

What everyone needs to know about water injection is that you have to be running AT LEAST 17 PSI. The water won't atomize well enough at lower pressures for this system to work. It's pretty widely used in the DSM circles. It only costs about $300 to install, and it's worth nearly a hundred horsepower on a properly tuned car. Amazing. Not only does it cool everything in the combustion chamber, but it also cleans everything out of the combustion chamber. Carbon won't stick to an engine that's running water injection. Most Hondas can't handle 17PSI on stock internals for very long (if at all). I don't think any OEM Honda head bolts could hold it either. You won't find water injection to be even a possibility with your Honda unless you LOWER its compression, enabling you to run higher boost.

There's a local guy whose name I forgot, but he has a blue Scubaru WRX wagon running low 12's. He's utilizing a pressure-activated home-made water sprayer setup on his IC core, and says the core has never heat soaked. Most of what made his car fast were hacks, but he pulled it off nicely. Overall it was a sweet setup. A lot faster than mine.

Just goes to show you that any one of those setups work. The reason any of these systems exist is to prevent heat soak. So basically, unless you're able to heat soak your FMIC, you don't need them, but in some ways you can still benefit from them.

If you get a intercooler sprayer that uses a gas, go for CO2 instead. Using nitrous oxide for that purpose is stupid. Either way, if the car is driven on the street, it will just be a fashion accessory. I'd reserve plans for that setup unless you spend every weekend at the track.