That's such a broad question. What are you looking for in an exhaust?

Some things to consider:

- Axleback or catback?
- Volume
- Tone
- Reliability
- Level of performance: low end torque? Mid range, at high revs? or just throughout the powerband
- Price: how much are you looking to spend or willing to spend up to?
- Size of the piping (ties in with performance)
- B-Piping design
- B-Pipe thickness
- B-Pipe material

I can come up with several few more variables but I'm tired as hell from work and class to think about it right now.