To answer your queoitsns:1. Yes, people have tried it and although some claim it works, there is no scientific evidence to prove that it does. How come some claim it does? Well because it is a giant scam which uses well-paid affiliates. These affiliates (very few of who actually have these systems in their cars) are told to lie about the system and claim they do have it. They make outrageous (untrue) claims such as it works for me, my gas mileage has improved from 18mpg to 28mpg since I fitted the device and direct people to a website where you're encouraged to buy a kit or book. If you're silly enough to do so, the affiliate earns around $25-$50 (50% of the sale price). So it's no wonder they lie.2. It is not hard at all to convert your car but it is a complete waste of time because these systems will actually *reduce* your fuel efficiency. See the link I've provided for the reasons why this is the case. You end up drawing more power from your engine than is returned by way of the gas that's generated and to create that extra power you have to burn even more fuel.3. It will neither increase the noise or power of your vehicle. In fact, you'll have *less* power because some of your HP will be wasted simply heating your alternator and the electrolysis cell (which can run 100 deg F or higher).4. There *can* be ill effects. If the hydrogen gas flashes back into the electrolysis cell this can explode and spray water (usually with a dilute acid or salt) around inside the engine bay wetting your electronics and electrics plus producing a risk of the electrolysis cell shorting and creating a fire).The best source I can suggest is the link below where the nature of the scam is described and there is some very simple math to prove why these things don't and can't work.Please read the pages involved in this article and also tell your friends just in case they might be tempted to get taken-in by these conmen.And remember if it sounds too good to be true, it almost certainly is.