Just before I rush over to TPS to buy one, can anyone tell me if I'm right in thinking my PCV has failed?  Loud squealing, as if a belt is knackered, and RPM all over the place.  Pull the oil dipstick out, rush of air, noise stops, engine splutters and almost dies. Put the disptick back in and puit your finger on the little hole on the right side of the PCV 'disc' and the noise gets even worse.     Knackered PCV?