Not to mention turbocharged 300hp engines and 300hp n/a engines are two different beasts. A turbo engine of the same power will outperform its na opponent in almost every case given same weight/gearing ect. The harder you push against a turbo, the harder it pushes back. So I would dare to say, a 250whp turbo 2.5L wrx will outpull a 250whp na 3.5L 350z at any point on the highway. Especially since the 06's are more aerodynamic than previous wrx's, and still weigh less than most models of the z.