As mentioned.. Riced out, or "Ricers" started in the 80s when kids pimped out, slammed, etc... their cars. They were typically Hondas, Toyotas, Mitsubishi's and Nissans... Asian cars, therefore the name. They were cheap to buy used and kids drove them and customized them to stand out. Somebody called it ricer, and it stuck. But you'll see Ford Focus's, Dodge Neons, etc done the same way. It's not a racial slam but a description of a style.
Lowriders, hot rods, muscle cars, motor heads..... and ricers.