[AzJared]

So i recently replaced my exhaust with a hks high power catback and no name headers a friend gave me. at first i only hooked up one 02 sensor cause i didn't have wire to extend the other and it would rarely sputter as i was steady on the gas in first. I extended the second sensor today and reset my check engine light, the light hasn't turned on since but it seems as though it sputters more often now, and only does it in first unless i accelerate fast. i thought it was just doing it being as i only had one sensor it but now i have no idea why anyone know what my problem is? Any help or things to check would be appreciated, thanks.