first let me list my set up for my exhaust atm. I have borla headers, randomtech highflow cat, apexi n1 cat-back. so about two weeks ago my check engine light came on i checked it out and it said it was my cat. ive had this cat on for less then a year so i really doubt this could be the problem. does this happen when the cat is replaced? or what could the problem be? maybe a leak im sure i have one since i reused gaskets. any info will help out thanks