I have a p0171 code that keeps popping back up. my wideband afr reads normal, not running lean. i just had my heads ported and polished at my local machine shop. they did a pretty good job and didnt open them up too much from what i could see. ive checked for vacuum leaks, nothing. i replaced my front o2 sensor, nothing. still have to try the egr tube. does anyone know if the ported heads could be causing this problem?