Ok so the other day my car threw a P0171 running lean bank 1. Car seemed to be running fine so I deleted it with my aeroforce thinking if it was running lean constantly it would come back right away, well it didnt until today (a couple days later). Ive been meaning to get a tune but I was waiting on a couple more parts so I didnt waste money on 2 tunes. Any ideas what it could be? Been told it could be the o2 sensor upfront, bad injector(s), fuel pump going bad, fuel filter clogged, or my car needs a tune with my mods to get more fuel. Well if you take a look at w body store headers the front o2 sensor only reads the front three cylinders so if it was the pump or filter it would happen to all the cylinders right? Just trying to figure out what it could be. I dont want to destroy my engine.