That is weird, do you mean the pcv valve? If so, reinsert the pcv valve and remove the oil filler cap. does it smooth out? Is the pcv valve good? this will at least tell you if its becaause of the pcv valve or the crank case presure.
I recently swapped motors in mine with one that sat for some time and the rings were stuck from sitting. So I remoived the plugs and shot some tranny fluid down into the cylinders and let it soak for a while .5 hour. then ran it some more. Let it heat up and then let it sit. after a while they free'd up and it ran smooth. I dont know if this is your problem, just something to concider.