No, it's not.

Entrapment by definition is "To lure into performing a previously or otherwise uncontemplated illegal act. "

The key word here is uncontemplated

Street racing is illegal. I know it is, you know it is, the officer knows it is. If the situation had been the same but the guy wasn't a cop, you would still have acted in the same manner, because prior to the cop turning on his lights, you didn't know it was a cop, therefore you would have been willingly participating in something illegal.

It would be entrapment if the person had said something like "if you don't race me, 50 kids will die", and you do, and then they bust you. Other than that, if you stoplight showdown with people, you're pretty much asking to get busted.