I am looking at purchasing an X-Pipe--do any of you have any insight into the following:

What type of HP/Torque gains can I expect? I currently have Borla Catbacks w/an SCT Tune(will I have to re-tune)

How loud over a catback system is it?

What is a typical install price at a performance shop?

or is an h-pie better, louder, produce more gains?

Thanks much