A “Yee Yee” truck is generally owned by country, hick, or redneck folk. Often times waving either a confederate or US flag.
Someone who is “Yee Yee” would fall into the country, hick or redneck category.
“I was driving and a yee yee truck kept tailgating me. Then he passed me and made the black smoke come out of his exhaust.”
“If you start waving around a confederate flag, people are gonna think you’re yee yee”