Have an 08 impala SS with 5.3 engine and when the key is completely turned to the off position it sounds like a pump or compressor running on and off all the time what could this be

What is your question?

Almost sounds like a air compressor or blender door ticking a lot when car is completely shut off and keys are out of the ignition what could cause this?

What makes this problem better or worse?

Nothing

How long has your 2014 Chevrolet Impala Limited had this problem?

Months