I have an 07 SS/SC tuned by Fred@SMG Motorsports up here in MA, but it seems that ever since it started getting colder I keep getting random P0171 CELs. It goes away by itself after a few days, but tends to come back when it's getting colder.

I tried switching gas brands but it came back even when running on Mobil Premium. My mods are Stg2 kit with custom tune and a GMPP Sport Exhaust. Prior to the custom tune (the Stg2 flash) I had no problems whatsoever.

Car has 74k MI on it so far, and everything else is still stock. So far the only major work that's been done has been the clutch (replaced the pos stock one with Spec Stg2+) and new rotors/pads. Clutch has been good for like 50k MI.

 

you might want to go get retuned for the winter the colder weather makes the car run leaner

 

check your maf, and make sure there's no leaks on your intake.

 

It seems your tune is to lean for the cold weather.
Have your afr checked by someone while its cold out ,your probably running lean.

 

doesn't necesarily mean you're lean. just like a cat code doesn't necesarily mean your cat isn't working. Just outside the parameters it's told to read. easiest and first step like i said is to check for leaks, and check your maf.