It is fuel injected so I know it's not the carburetor however I never thought of the pvc valve . If I shake it should it rattle. It's been so long I can remember. The ignitor did help now it doesn't sound like its underwater any more or at least it hasn't repeated itself. Now it seems to want to die and then it's just fine again. The engine typically runs for 2-5 hrs at 2500 rpms under a heavy load . Then on to the next job and repeat. It's a ghost problem I can't make it happen and now it last for less then 1 minute and solves itself. I did go ahead and replace the spark plugs with NGK gr4 gapped at 44. It still has the original coil and wires but they seems fine. It has been the best engine I ever owned . Does it use a standard 12 volt coil. No harm in replacing it.

Gene