20hp... idk about that oneHave both! I would recommend both but the high flow cat converter is a must if u wanta see those gains. With both, and without the dyno loss, it's about a 20 HP gain. I don't know if you'll get the true sense of the CAI if you put it in at the same time as the exhaust but the CAI alone makes the car sound awesome. I've had my CAI for a while now and love it and just got the exhaust a few days ago and am in love get the burnt tips too!