Codes p0171 and p0174

[Ldub]

Just cleared out my 171 and 174 codes this weekend. An intake tear down and a solid blast of MAF cleaner did the trick. Did not bother with the o2 sensors. I just passed emissions about 3 weeks ago (CEL didnt spawn until 2 days after I passed, heh), so I am in no immediate hurry. I will just wait and see if the sensors themselves decide to throw a CEL (I believe that is a 420 if I am not mistaken).

Thought this may be related at first since both popped up about the same time, but it does not appear so. Even after cleaning the MAF and clearing the codes, my VX is still running.... funky. On cold startup, it idles at roughly 2k-2300k. On warm startup, sometimes it simply stalls at idle unless given some juice. This is all new as the S/C has been in for almost 2 years now. I am leaning towards the FPR and/or the EGR. Both were fully prepped and cleaned when I installed my S/C, but considering I have 7 hard years on both, it wouldn't hurt to replace. It may also be one of the reasons why the VX has started to run a bit lean and is suffering minor fuel dump. Thoughts?

FPR could be a contributing factor, especially if you didn't pop in a new one when you installed the S-C. BTW, you can get a right angle snap ring pliers that JUST has enough clearance, at Harbor Freight for cheap...
The one I got has straight, 45 deg. & 90 deg. interchangable jaws.
Also, the snap ring that comes with a new FPR is too small for the aluminium block on the S-C kit, so re-use the old one.
The lean condition that the codes are indicating, from my past experience, points towards a vacuum leak, either intake gaskets or vac. line.
I've had vac. lines pop off under boost, also check the PCV valve & hose, I recently had the same exact symptoms & it turned out that I had a bad PCV valve. (the top & bottom had come apart)