My 2006 is showing a check engine light and i took it to the dealer where i work and they said it was a fuel trim code and it was running lean. At the time i had a hole in the muffler and they said that the lack of backpressure might cause the the tripping of the code. i have replaced the muffler since then and the light is still on. Does anyone know what might be causeing this and if i can fix it myself.