I got the codes p0171 and p0174 on my 03 5.4 Supercharged Harley. I had no drivability issues at all but after cleaning my MAF the codes came back. SOLUTION: I didn't hear any hissing but went ahead and followed the PCV hose that goes to the back center of the engine and removed the
90 degree rubber the connects to the block and it was indeed colapsed. It is very hard to get to especially if u have large arms you may need the assistance of a skinny helper. I did use a spark plug wire boot and it seems to work well................. I just wanted to share this info because after many hours of research I could not find anything for the supercharged engines. I hope I can at least help one person and save them a few $ and alot of headaches. Thanks for listening!
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Code's are Lean Bank 1 and 2, I have seen Several Problems cause this Vacuum leak, I asume you pluged the lower part of the intake behind engine These crack all the time,( Very Hard to get to) O2 sencor can cause this,Good Luck

 

I have a 03 Lightning myself and found the PCV valve on the passenger side valve cover. I don't have any problems or anything but wanted to say that, with supercharged engines, you would hope that the PCV valve itself is a bi-directional unit.

Otherwise, unless you have an oil recovery system, there would be MORE oil comming up into the intake than normal. A normal ammount is just a slight sheen coating of oil inside the intake and around the throttle body.

Motorcraft EV-233 PCV valve is stock on the 03 Lightnings and IS bi-directional. They also come with a 45 degree boot that you can take off. I installed PCV valve w/45 degree boot and it does calapse. Just remove the boot and install it straight up (2003 Lightning here) and all is well.

King Leo