I was looking through some past threads, and saw that a few people had the Check Engine Light go on after the K&N install. Who all had this happen, mine is on right now. I think this same thing happened after I changed the air filter, and it went off the next morning. I did unhook the battery while putting it in, and I noticed one other person stated he did as well, also getting the CEL. Same with the filter, I unhooked the battery and it came on when I started it back up. I'm hoping it will go back off in the morning like last time... if you did get the light, did you also unhook the battery?