I had a similar experience a few months ago. Someone in a new Civic Si was behind me right before a left-hand turn (2 lanes wide) from FM 78, which is also a freeway entrance for I410 South and I35 South. About 300 yards in on the ramp, there is traffic which is entering this ramp from the left, from I410, and must be yielded to. I was ahead of the Civic, and punched it to avoid the folks coming in from the left. He wasn't able to hang with me, and had to slow down for that traffic. Up ahead, the ramp curves to the right, straightens for a bit, then curves left before merging with I35. I had eased back to cruise mode, but looked in the mirror to see the Civic catching up with me. After completing the right sweeper, I sped up a little before the left, but not by too much. Mr. Civic was hell-bent on getting past me, and I wanted to see what he had. I stayed in the right lane, he moved to the inside left lane, balls-to-the-walls, passing me up! I quickly matched his speed, but couldn't pass him, there was a slower car in my lane, and both lanes were fixing to merge into one. He blew by the slower car, and I stayed back to wait until we're on the HWY. Once on I35, I caught up and paced him, easily keeping up. Traffic prevented any real passing situation, but Mr. Civic decided to start weaving through folks like he was playing some video game. I just let him go, vowing for payback some other day. That was about 4 or 5 months ago, and I haven't seem hide nor hair of him since.