I was getting ready to start installing the LM34 temperature sensor into the air cleaner and decided to pull out the original MAT sensor that Edelbrock buried behind and underneath the air horn.  When I had relocated the MAT sensor a number of years ago I left the original one in place because I couldn't get at it.  At this time I was only a couple bolts away so I elected to pull off the air horn to remove the sensor.  Needless to say I was a bit surprised as to what I found underneath it.  One big guey carbon mess.  Apparently this is a common problem with port injection.  After the motor is stopped fuel is carbonized on the inside of the manifold as the motor heat soaks.  What is not clear to me is where all his fuel comes from.  I can believe the heat soak part because it gets might hot under the hood and when the car stops moving the temperatures go through the roof.  I hate to see what the top of the intake valves are like.