To throw 171 aka lean bank 1 you need to have been out of the acceptable range 3 consecutive time running. This means you are over 16.4% fuelling being added by the pcm. So it's telling you.
Flashing CEL means that the PCM sees a potential catalyst damaging condition aka you had misfires based on the code.
From what you are saying.. it sounds like you have a vacuum leak. You did the right thing, you checked for a vacuum leak. Except, there's one smaller leak that you can never find with starter fluid. Remove the pipe from the EGR to LIM and pull back the retaining piece, then look where the retainer would hold the lip for cracks. Likely...it's cracked, 90% of them are cracked.
Now that's not giving you enough to go on for a true fix. Let's jump in deeper and talk about fuelling. 41 at idle is fine in my experience for the average SC motor. Does the pressure increase properly when you remove the vacuum from the FPR? What does the fueling do when you are driving? (I made an extension pressure hose).
Keep in mind that the swivelling plastic piece in the hose at the brake booster is also a check valve. Shouldn't be an issue, I have seen one or two cause a problem though.
