I hooked up with a mitsu WRX prepped up on the highway here in France, and ha was all over my ass from the 100mph to 125mph but he was aspirating and couldn't cut the pass...from 125 up i started to pull..theres about a 100lb difference,,in his favor but if he walked away,even on a stock Z, maybe yer Z needs a little tune up...although I've had porsches give me less headaches than those cars.....