I would go with the Novarossi 2630 tuned pipe as it was designed for Novarossi engines. The different conical fin headers are for low end and high end performance. Someone may correct me on this but I believe there are 3, 4, 5, 6 and 7 fin conical headers available for the Novarossi 2630 tuned pipe. This aollows for a wide range of tuning based on whether you are running on a short, medium or long track and if your looking for more low end power or top end speed.

Regards,
Speyederjedi