Driving so slow but BK is from Texas
He’s driving with Beyonce (Knowles), who is from Texas. He feels the need to point this out because slowness is associated with Houston-style rap, which is “chopped and screwed”, i.e. slowed down to the point a person fucked up on Codeine can follow it
Also, driving slow aka “Tippin'” is a trend in Houston — it’s considered a way of showing off your fancy rims (while avoiding speeding tickets! Smart..)