Replace two thumping SRV valves this week on the same job. The PGV tops fit the SRV valve body so it is an easy fix...After thinking about the problem I believe it is the solenoid not opening all the way. Pulled out my calipers and measured the solenoid hole on both valve tops. The SRV is 2/100th" smaller than the PGV... Same measurements on a few different valve tops, all the same.