1995 Ford Probe Noise from engine when accelerating or rev

Hi,

Am looking at a 95 Ford Probe with 166,000kms which I beileve is about 104,000 miles. Anyway, when revving the car as it is stationary to about 2000/3000 rpm? The car starts making this rattling metalic noice that sounds something like someone shaking a can of nails, the noise goes away as the car stops revving, and also disappears when cruising along highways, or when cruising along at high speed the noise is also not present, can't really explain it, but it very noticeable on revving and when accellerating, car hasn't been used for a couple of weeks and white smoke comes out from the exhaust, but no oil, however, there is water. Not sure if this is related. There doesn't seem to be any other issues or noises that I have noticed, could this be a serious problem? Your help really appreciated.

Thanks.