[Formulajones]

I wouldn't go chasing exhaust. In Your case it's not an issue.

I ran Gardner exhaust on my RAIII in pure stock and ran 14 flat with it at 99 mph. While it wasn't holding the car back a ton it wasn't a pig either at a 3890 race weight

I did switch to a flowmaster transverse setup back then because 2 1/2" is legal and what most run in the class, and ran 13.70's at 102 mph with no other changes. Worth maybe 30 hp or so. Don't think that's your issue when you say it's a pig.