I recently raced my Sti and right after I noticed I had a code come on I pulled over to check it and it was a P0171 code. I need help diagnosing it. I’ve checked my air intank it was all good my MAF sensor was good. My o2 sensor on the down pipe had some white residue it looked like. I just ordered a perinn fuel pressure regulator and will be swapping the stock one out.