Getting an P0455 on GMC. Most mentioned it was common Evap code and to replace purge solenoid and or Evap purge valve. They were marked on the box as such but I took both pieces out and they looked exactly the same. I installed the Solenoid in the front/top engine, just a little clip kept it in, pretty easy. Where does the evap purge valve go and is it inside or attached to the evap cannister? Are they the same part-evap purge valve and purge solenoid- just in different locations? Could someone give me the "kids book" version of their function and help me with this?