Buy a 3" rubber coupling for cast iron piping from a local hardware store lowe's or home depot. The ones with the hose clamps on each end. Cut it to the length you need then soften it to stretch around the CAI tubing. I used the microwave for about 45 seconds checking every 15s and stretching. Worked for me and still works to this day.
2012 Mustang Club of America Edition Silver Ingot V6 Premium, 6MT, BBK Shorty Headers, Mak Performance catless H-Pipe (not MAC), Magnaflow Street Catback, Airaid CAI, MPT 93R Tune, 80mm Throttle Body, Ported Intake Manifolds, SR Lowering Springs, SR Adjustable Panhard Bar, Lakewood 50/50 Shocks, Steeda Heavy Duty Strut Mounts.