Just finished doing the plenum gasket repair to fix the P0171 and P0174. It went pretty smooth and car is running as it used to. Less than 100 miles after I finished that I threw the P0174 code and that one doesn't look like fun. I cleared all the codes and monitored them until the P0174 was gone from history. Could this have shown up as some kind of fluke from when I fixed the plenum? It hasn't come back for a couple hundred miles.