A dual with an x-pipe seems to be the most popular suggestion. I know for a fact the single flowmaster doesn't flow enough. I have a two-chamber single in/dual out and it is choking the shit out of my engine right now. It doesn't even sound like a flowmaster under full throttle. I need some serious exhaust work also. When I go true dual, i'll probably stay with flowmaster. They don't flow as well as other mufflers, but i'd like to keep a little backpressure for low end.
2003 Arrival Blue Silverado SS.....I just can't leave $hit alone.