The whole grill is roadkill,
A “grill” is a gold/diamond piece that goes over one’s teeth; it was popularized by several important Houston and New Orleans rappers in the early 2000s. Lupe’s criticism of these accessories, and the commercial style of music they are associated with, ties in to his car metaphor, since the “grill” is also the front of an automobile.
He could also be saying that his whole grill (on his “car”) is covered in roadkill (other rappers that he “runs over”). The last part of the explanation of the previous line seems to back this up.
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