Sorry for the late response. Yes, it did resolve the issue.

I just had Sears do an oil change and change my plugs at ~96k w/ Iridium and Platinum plugs. I am now getting the P0171 error when I didn't before.

P0171 DTC: System Too Lean

I guess I'll check my K&N and then call Sears.

First: This thread is OLD.

Next: If sears did not use AC Delco plugs, then you just wasted $$ on having them put in crap that will be fried in short order. This has been said here and at other Hummer, Colorado and Canyon forums before: If you have an I5 do not use anything but AC Delco plugs or you are asking for trouble.

All I did was use Search. It's not like I spent hours digging thru old posts. Anyways, I did have Search swap out the plugs for AC Delco Iridium.

I still am getting the error though.

I noticed people were saying to look at the intake, MAF, etc. The fat foam seal that goes out to the firewall seems fine and the intake box where my K&N is seems fine.

I did notice that there's a hose up near the hinge of my engine that was just sitting there. "1/2 GM6148-M 090505 AGB'. It seems like it could be the air intake vacuum line. Whether it's actually from my car or not we'll see but I think it's likely the culprit as people were saying it's possibly a vac leak.

Does this hose look familiar to anyone?

it's pretty strange as the car seems to run ok.

That hose was from the stock intake (underneath rear of the resonator box) to the breather port at the rear of the valve cover. Whoever put on your K&N must have left it there.

K&Ns also have a rep for cracking, cracks leak.

The intake manifold bolts that fasten it the head have been known to vibrate loose and cause a leak.

Interesting. Thanks! :)

Check your breather hose. Mine was disconnected.
Took a Zip tie and locked then hose to the box, then slipped the other side to the crankcase port. No more code and an easier install.

Yup for me it was the hose. somehow one of them took it off when doing my plugs. they put it back on and everything was fine again. thanks