Yes, it exists. It is littel more than a windshield washer bottle, a nozzle and a switch on the accelerator to switch on the system when at WOT.

I wouldn't bother installing it since the only advantage is less chance of detonation (when running much ignition advance) by cooling down the mixture (which can also give a little higher density). A perfect setup could maybe give you 2 or 3 more hp but 20% improvement isn't possible on a NA engine. If it really worked that well everyone would have one.

Best regards.