Does anyone know what this means?
 

My 2001 i30 lately after I warm it up and put it in drive orreverse the rpms are around between 500-600 and after I press the gas a little it and go down the road itgoes back to normal. Why do they drop so low after me warming up the car? I used to have a system in but I took it out. Does that have anything to do with it? Could it be voltage regulator?

may be a bit low.. but only by a 100 rpms or so... :gotme:

My max revs around there when warm, as well.