two problems- related?

i have a 2004 ford focus zx3 with around 20,000 miles on it.

problem #1:
my car sometimes stalls when im slowing down. several of the warning lights on my dash come on and then the car just dies and i have to re-start it. ive been told that this could be the result of accidentally getting water in my engine via my CAI but im not sure if i buy that. anyone else have this problem, and more importantly, anyone know how to fix it?

problem #2:
my electrical system randomly "browns out". my headlights go out, my ac cuts off, my radio dies, my spedometer, fuel gauge and tach all drop to zero. this did not happen when i first bought the car. i have a 400 watt system that may be the cause of this problem, i dont know.

i cant really take the car in to get the shop to fix these problems because theyre not reliable and i cant just snap my fingers and make my car do this crap to show the car doctors whats goin on so they can fix it. theres no regularity at all here- some days i can drive around for hours without having problems, and other days this stuff is happening every 5 minutes or less.

help would be greatly appreciated

I've seen problem 1 before on other cars, and the cause was usually a bad throttle position sensor...I doubt that any water caused it. If it wasn't for the CAI, you could take it to the dealer and it would be a warrenty claim, but the dealer would probably claim that your powertrain warrenty, (anything electrical too) is void because of your mods.