Should the PCV valve be making clicking noise at idle?

I have a 1993 gmc sierra that has a chevy 350 engine. Whenever my truck is idling/parked the PCV valve makes a clicking/tapping noise as if the valve is opening and closing. I have tried to replace the valve two times and the grommet that holds it, it is also a brand new vacuum line into the TBI. I cant seem to think that this is normal because my 1990 of the same truck never seemed to do this. What are some things i should check for or do?