[venturaII]

I recently installed an aftermarket catback on my '13 FRS (90k miles, all stock drivetrain), and with the slightly louder exhaust note now, I've noticed a light, brief stumble every time I shift gears, or tip into the throttle very lightly after coasting. It's most noticeable at lower rpms, when I'm just putting around town and shifting around 3k rpm. I just did an OBD scan and there's no codes stored, so I'm a little puzzled. I'm not sure how long it's been doing it since I can only really hear it and not feel it... I'm going to be taking the car on a 2000 mile trip in a couple of weeks, so I really don't want this to turn into a problem out on the road somewhere. I did a quick search on a few obvious keywords, but nothing close came up. Has anyone else experienced this? It it indicative of an upcoming failure?

Thanks -