93 mercury sable 3.8L, car runs fine for short trips, but longer than an hour and half, the car goes to a lean condition, backfires through the intake and shuts off, let it cool its fine again. I got codes of 157 mass air flow sensor below min volt, 172 ho2s system indicates lean, 176 system indicates lean and 327 egr circuit below min volt. Check Engine light doesn't stay on, and only those codes are in CM. Should I replace the maf sensor, egr and o2 sensors? Or could there be another underlying problem to throw those codes?