Engine misfiring, running real rough, code 41

I have the car listed above EX with a 2.4 vtec. By the way this might not make a difference but the car sat for 11 years, never started even once during that time it sat. The day I tried to start it, put some gas in intake started right up. Okay, anyways the other day had my family in car so it was kinda low to the ground, I drive up a driveway and tore the muffler right off. I didn't have time to put it back on, so I drove it for a whole day with no muffler. Yesterday I finally reattached it, drove a little while. Next morning on the highway engine started running real rough had to shut off A/C. Got a code 41. Any help would be really appreciated.