Just listen to the motor, not the muffler..
Many clear signs tell the power of the car. Rice rockets listen to see if they gasp for air, or the whine of a charger. If the guy is an idot see if he will rev it up and listen for the turbo. Cars like yours they can sound mean, the key is if the motor hits smooth and the car rocks at an idot, it has real power. Not always a sure way to tell but a good ear can really help.
I have built a few toys my fav was a 1986 Monte, built her a 386 roller motor, 6.6 144 1/8. That comes out to about a 10 second 1/4 street legal car running cut 12" slicks. I never got beat by a single street legal rice rocket. I have been spanked by a few big blocks and super charged 350 svo stangs that I thought if I could get the jump I might have a chance.... but no
I got hard tricked by a new transam once, it was so quite it sounded stock. He hit the dumps, poped the bottle and the rpms hit and it was nothing but blower.. The race hadn't started and I knew I was fucked and out $100.