I have a 95 Ram 1500 318 V8 Magnum, it smokes and it vibrates at speeds between 45-50. I changed the PCV valve because it was clogged and sprayed oil out of my dipstick, and it coated everything, especially my breather and air filter. It has a miss in the engine too. I know you are busy. Thank you.
Even though you changed the PCV valve you would still need vacuum at the PCV valve. If there is not any vacuum check the hose for any leak or clog that could block the vacuum from getting to the valve. If the hose is clear then the vacuum port in the intake manifold is probably clogged with sludge. Try using a wire to unclog the port while the engine is running it will help you determine when the port is open you will hear the vacuum when it is clear.
Locate the cylinder that is malfunctioning and determine why it is faulty. If the spark plug is fouled determine whether it is oil, gas or coolant.
Look at the smoke; black smoke indicates excessive gas.
White smoke would be antifreeze and blue smoke would be oil.
You may have to remove the valve covers to see if the oil drain holes in the head are not clogged with sludge, if they are try to unclog them with out having the sludge go into the bottom of the engine. Try using a wet vac while unclogging the holes it is helpful while clearing the drain holes.
Try these suggestions and get back to me with your results.