Got the P0171...

[rkvons]

So I have a '98 GTP and recently got the P0171. Bank 1 too lean, or something. Oh, and this is my first code since owning the car new in 1998!
Here are statistics:
~77K miles. Only thing I've really changed under the hood so far is filters and oil. Did a water pump (because I thought it was going bad), and then did the SC coupler afterwards (because that was going bad). I've also replaced the battery.

I've read the list of things to do, which is as follows (Thanks BNaylor):

Here is the course of action per the GM service manual:

Check all vacuum hoses at intake system.
PCV Valve
Possible throttle body blockage (clean input screen and body)
IAC (idle air controller valve)
Check fuel injectors (bad o-ring seal)
MAF sensor
EGR valve
Check 02 sensor (Front)
Contaminated fuel

I want to do the first thing on the list and have never had any luck looking at hoses to see if they are leaking, so I would like to spray carb cleaner around there to see if anything changes and also put a vacuum gauge on it. The question is, where do I connect the vacuum gauge? Also, what vacuum should I see at idle? Any other thoughts or suggestions will be appreciated. Thanks.

[inafogg]

''77K miles. Only thing I've really changed under the hood so far is filters and oil''
i hope filters included fuel filters

[TDWPgtp]

when that happened to me it ended up being the fuel pump i believe. several mechanics told me it wasnt the fuel pump and kept trying different things, then finally it ended up being the fuel pump...it happened around 80k on me too. good luck finding your problem! i hope this helped

[rkvons]

Originally Posted by inafogg

i hope filters included fuel filters

No, have not changed the fuel filter yet.

The light went out on my way in to work this morning.

[rkvons]

Originally Posted by rkvons

The question is, where do I connect the vacuum gauge? Also, what vacuum should I see at idle?

Must have been a stupid question...

[inafogg]

pull any vacuum line from the intake & hook gauge in there
just make sure there is vacuum when you pull hose off
about 14 - 17 i think

[BNaylor]

14-17 is way too low. Should be around 18-22 in-hg

Best to use the vacuum lines off the throttle body or tee into where the MAP sensor vacuum lines are at the Upper Intake Manifold which obviously is the supercharger. Under the snout area.

BTW - An exhaust system leak close to the front pre-CAT 02 sensor can cause a P0171 DTC to set.