I have a 07' Corolla with the engine code P0171. I hear a low whistle when accelerating. (Like a vacuum leak) 192k miles. Looked under the hood and nothing seems to be loose or out of place.
Thanks.
Oftentimes, a P0171 means that your Toyota is having trouble with a dirty or faulty mass air flow (MAF) sensor, or a vacuum leak downstream of the MAF sensor (perhaps in the PCV line or in the valve itself). Of course, this code can also signify a bad O2 sensor in bank 1.
Scotty recommends cleaning your MAF sensor and throttle with spray cleaner per this video