Hello, I have a 97 K1500 with a 5.7. I am at a loss for an issue that arose today upon a heavy acceleration this occurred out of nowhere and now will not go away. Rough idle almost like a miss at idle, upon acceleration out backfires through the exhaust. The two codes that were thrown when this problem began were an intermittent P0175 (fuel trim system rich bank two) and a non intermittent P0420 (catalyst system low efficiency bank 1). The truck runs horrible and backfires severely under load.any help would be a blessing.