the extremes and flow-10s are single chamber mufflers... sound absolutly wild! the extremes are basiclly a copy of the flows, i used to have a set but not anymore... post a sound clip when you get them!
If you can weld, I have a pair of flow master 2 chambers with low use. They are 10 years old but only were on the car for 4000 miles or so.
Downside is whoever cut them off cut them too close to the muffler and didn't leave much tube. I'll let em go cheap but might be Some work to get them on.