Hello. I have a 1996 Blazer with 4.3L engine that hesitates on acceleration. Sitting at idle and punch the accelerator, engine bogs down and then accelerates. No check engine light comes on. Also, PCV valve vibrates like crazy even after I replaced it. If I pull the PCV valve off, there is lots of vacuum at idle and if I plug the end with my thumb, it will kill the engine. I have replaced the distributor cap, rotor, spark plugs, wires, fuel filter, fuel pump last year. Not sure what direction to take now. Thanks for any help.