My 07 Sierra W/T Classic with the 4.3L engine threw the P0449 code (Evaporative Vent Solenoid). My son went to our local Advance Auto Parts store to pick up the necessary parts. The folks there wanted to know if my truck had the split headlight assembly or the solid headlight assembly in order to provide the correct part. Can someone help me out with this dilemma? Which does my truck have? An also advise why the headlight assembly makes a difference?