I have a xhance to get a dual cat exhuast for my car. Includes Y pipes but no muffler (I'll pick up a flowmaster or something)

Has anyone with a TBI ever done this?

Can anyone outline any differences between the 2 systems?

Would a 20hp gain be a reasonable estimate?

AND....are the exhaust manifolds any different?

 

It has been done, althought I'm not sure if it was the tpi single or dual cat exhaust, but either way it made 12 rwhp on the dyno. Yes the exhaust manifolds are bigger and flow better. I would just get headers though.