i recently took my 02 wrx into a local stealership for the fuel line recall. They completely the recall and not 5 miles down the road the cel comes on. I took it to my work and scanned the code with my pocket scanner and the code was p0031- front a/f sensor heater circuit low imput. i put a new sensor in it but nothing, still a hard fault even after cleared. i hastely returned to the stealership and told them all of this and they told me that there was absolutely no way that could of been caused by their repairs. Ive had the car for a little over a year and a half and never any problems but 5 miles after they "fix" it this happens. They told me there was probably a short somewhere in the harness. They refuse to fix it as well. My question is this: if i install a catless/sensorless uppipe and get a protune, could there be a set a/f ratio and would the ecm completely ignore this problem?