Weird feedback after head unit install

Hey everyone. I just installed a Blitz audio reciever for my girlfriend (I know, I know, but it was cheap, and she just wanted a cd player), and it has some really weird behavior. Firstly, when you turn the car on, you hear this loud (not really loud, but easily noticeable) buzzing sound that only goes away when you turn on the headlights. I have no idea on that one... I also seem to hear a high pitched whizzing noise when the lights ARE on, but it's far less noticeable. I think I might be hearing the engine sucking air, but I don't know. Anyway, any ideas on this? It sounds like there might be some interference or something... Thanks for any insight. Matt

oh yeah the actual unit is a BZC-1802mp and her car is a 2001 Suzuki Esteem.

anyone?

Well...I did some researching, and I think I've found what the high pitched whizzing noise is. Apparently, alternator AC switching causes interference sometimes, and the noise increases in pitch as the car accelerates and shifts. However, I don't know why her factory unit wouldn't have the same problem. There's no amplifier or equalizer installed, and no RCA outs are in use, so I don't really know what the problem could be, but it sounds like alternator interference. Anyone know how to fix this?

put a noise filter on the constant wire, or go to the ignition or battery for a constant source of 12+.  should help a whole lot, but dont forget to fuse it.  also, it can help to reground the unit somewhere else because sometimes the ground spot for the factory radio wiring is shared with a bunch of other crap and the unit can pick up noise.

There was a ground wire with a loop connector at the end of it, so I just used a wire tap to link the ground from the original wire to the unit's ground wire, and then grounded the two to a screw behind the unit. I'll try and reground the unit seperately and look at noise filters and see if anything helps.

Alright, well, I picked another point to reground, and it took care of most of the noise. There's still just a little buzz, but it's barely noticeable. It is, after all, a very cheap unit. The only thing I still notice s a "boom" noise everytime I hit the brakes. Interestingly enough, I think there might be an incurable electrical problem with the car itself, or maybe the unit itself. At night, when the A/C compressor kicks in, or you hit the brakes, you notice a slight drop in the brightness of the headlights. When this drop occurs, you also hear the boom noise. Don't know what that could be... Anyway, thanks for your help everyone.