I had dual supertrapps on my ZR2.

I like them, they're highly tunable, both sound and performance. They are a bit pricey however, and depending on your setup they take a better than average muffler shop to do the install.

My setup was dual Trapps exiting through my Rollpan.

4.3 liter V6, Sound was pretty loud, based on how I tuned it. Performance wasn't great at first, but after a short break in period they really helped out.