I'd never tag onto a fast car that was giving it some because they they could most likely stop quicker, handle better or even drive better. Meeting a car at the lights and having a short burst of acceleration say 0-60, is not going to start a war. Know your limits,your cars limits and keep an eye on fast eddy in his more powerful car. He may own a fast or expensive car, but it doesn't mean he/she can drive well either.