This is normal behaviour. I drove 5.0 Mustangs for years and the most common "wanna race?" guys were other 5.0 Mustangs. We'd get it on and then at the next light as, "Which gear you got, what mods." Almost ALL Mustangs are modded. It's as much comraderie as competition.
If someone pulls up in a hot 'benz, give 'em the thumbs up, but realize that may be taken as a sign that you want to race. A polite wave means "no thanks."
Remember, no matter how strong your skills, street racing is very dangerous because you have no idea of the skills and judgement of the other driver. I've looked in my mirror more than once and seen someone spinning behind me (even on a straight). Hence, I try to resist. If I can't, then it's a very short blast and then off. I'd much rather take a timed track run or AutoX run.
If you can't resist, remember that against a 'benz or 'stang you need RPM or you're toast. M3s are actually more demanding when it comes to getting max acceleration.