I received the following codes the other day after my CEL came on:
MIL: On
Diagnostic Trouble Codes
P0171 System Too Lean (Bank 1)
P0174 System Too Lean (Bank 2)
The car had been at the airport for about 5 days so I thought maybe this had something to do with it:dunno. I reset the CEL and now this morning ran another test and the same codes are now being shown as pending which means that the CEL light will be coming on soon.

I'm at 82K miles and I have plenty of gas in the tank and haven't done any mods.

I've seen suggestions ranging from Vacuum leak, MAF sensor, 02 sensor, any ideads on where to start.

Car seems to be running fine.

Running lean is most likely to be the result of one (or more) of:

1) Intake leak
2) Insufficient fuel pressure/volume (clogged filter, bad pump, or bad fuel pressure regulator)
3) Defective MAF (quite likely if the car has an oiled air filter like with a CAI)

It is possible that the pre-cat O2 sensors have aged enough to indicate an abnormally lean condition, but the odds of both (one for each bank) reaching that condition at the same time are pretty low. And the usual symptom of aged pre-cat O2 sensors is a "Fuel Trim" fault. However, your mileage is in the range where replacement of the pre-cat O2 sensors is indicated even if they aren't causing a noticable fault.

If it were mine I'd replace the pre-cat O2 sensors now or within the next 10k on general principles. To resolve those fault codes I'd start by looking for an intake leak and working down the list.

Dont forget to check for very dirty air filter, PCV system, all vacuum hoses and the intake tract between the MAF and throttle body. Basically if unmetered air is getting into the intake it will throw the lean codes.

Is there a link that could tell me every place to check for an intake leak.

Or is it time to get that Bentley Manual?

Is there a link that could tell me every place to check for an intake leak.
Or is it time to get that Bentley Manual?
It is really just common sense. Check every hose and connection between the MAF and the head. Or, take it to a shop that is equipped to do a smoke test.

Didn't notice any leaks, changed plugs Thursday night and so far the light hasn't returned. Maybe it took care of itself?

http://www.obd-codes.com/trouble_codes/generic/p0171-system-too-lean-bank-1-oxygen-sensor.php

http://www.obd-codes.com/trouble_codes/generic/p0174-system-too-lean-bank-2-oxygen-sensor.php

Just an update on this, I changed the plugs about three weeks ago and the error code has not reappeared since.

I think it will someday but as of today all is good, keep the fingers crossed.

Maybe the problem just fixed itself?

Just an update on this, I changed the plugs about three weeks ago and the error code has not reappeared since.

I think it will someday but as of today all is good, keep the fingers crossed.

Maybe the problem just fixed itself?

Further update light had turned on a few times since, I kept restting it as car ran fine, then earlier in the week the light came back on and the car was very rough at idle.

I changed the elbow tube just before the throttle body intake (noticed a very small tear)$20 and car was idleing smoothly after the install.

I'll keep you updated if it happens again, but if it does then I'll probably just take the car in because my next suspect is the MAF sensor and those aren't $20.

Well finally took it in, it turned out to be the DISA valve which has an ring/gasket built into it where it meets the intake manifold. Over time this gasket had worn down and was letting air in.

Here's the real oem description and p/n

07 ADJUSTER UNIT 1 11617544805 $210.92


Parts and labor was just under $300

The car would ping very slightly under wide open throttle before on certain occasions, but since this repair I can't hear the least bit of pinging.

would it ping on idle too?