egr smoke gas smell

Dumb question of the day... Is the EGR valve control solenoid supposed to make a noise after I turn the truck off? It’s tough to describe but it’s a buzzing sound that lasts 1-2 seconds. Getting code 31. Also looking for vacuum leaks. ‘86 STX with 2.9 Thanks all!

I have a tailpipe putting out some black smoke and occasionally some gasoline smell. also idles some what rough. Could this be the O2 sensors or somehing to do with the EGR system. I ran the codes without a meter and got what I beleive a 166 or 167 or a 66 or 67. Thanks for help.