Unhook the hose from the PCV and block the hose off (vacuum leak) and your crankcase vacuum should be gone if that's the problem.

 

I've tried that but i still get alot of suction from the crankcase... I dont know why it does it. This is my video of the truck.... i just threw it together so you can see what its doing. check it out its pretty amusing, now whenever you see the MAF readings dip thats when i removed the pcv hose but i didnt take it away for too long because it would cause the engine to die so i tried to keep it in range so it could keep running.

 

2006 F250 5.4 XL with crank windows.... My symptom was an irritating bird chirping sound. It started the day I had a shop change all my plugs and coil packs for $500 total including Motorcraft Parts (well worth it to me on this motor). My assumption was oh great now I gotta replace tension and idler pulleys and belt. Which I did and needed to anyway at 117KMiles. Still chirping like a bird. I don't know what made me fiddle with the oil cap other than maybe thinking it was a lifter... Anyway after pulling the oil cap the chirping stopped but, the suction was great from the oil filler and I said self that is not normal. It did not die, I quickly replace the oil cap so as not to suck bugs in... Then I started researching and found horrifying things like cam phasers, stuck valves, cracked head, and exhaust leaks... The truck ran fine at speed and did not chirping at drive speed. So I ruled out mechanical all together. That much suction was not normal though. I keep researching. after thirty clicks I found this thread and the mechanics that did my plugs and coils had indeed by accident on the passenger side hooked up the PCV (vent) and EVAP backwards. The green tabbed connector hose/line goes from the EVAP and to intake manifold, I actually have no PCV per sei, it is just a vent port that goes to the air intake like the picture said. The picture that said here was my solution. Thanks Arizona Tumbleweed! for leading me to the water & I drank the water!

 

my port on my passenger side valve cover was clogged up. Im agreeing it's one side or the other that's clogged

 

I don't know if the poster ever fixed it or came back with a resolution. But he did mention a catch can for oil . We didn't see any pictures of it or the connections . As far as I know there was no factory catch cans in 2006 5.4l . But yet he said it was all factory . He also stated he didn't have a charcoal canister . Well he may not have known about it on the rear axle or the purge valve on the firewall . But I believe someone added the catch can and messed up the purge vac line and the filter air line to the passenger valve cover .
I don't believe any of these engines didn't have the purge valve on firewall , must have for emissions flex fuel or not . It has been stated that the only difference on flex fuel is the resistance of the lines to alcohol and workers stated they all had the same lines .
I know some guys added the catch can on passenger side to trap intake moisture and one on drivers side to catch oil ? If I tried it I would have put one in drivers side for oil . But space is limited and then there is a problem with super cold air on catch can freezing .
Very interesting problem ,I have to believe in those that had similar it was reversed lines on theirs .All this oil damage to his cats and a large amount in intake adds to that reversal theory or perhaps some bandit hook up to capped off throttle body fittings . I just wish I could have been there to mess with it . Excuse my rant .

 

Robert im having the same problem and mine is not flex fuel

 

I blocked off the pcv heater and hose then the truck ran great