P0012 and P0022
My 04 5.4l 3V Screw started throwing the P0012 ans P0022 codes. The motor has 120k but has always ran strong with no problems. I had a trans with 15k miles put in it at around 110k. should I put new heads on and if so, what are my options? What are my options to replace the engine? What year engines would be plug-n-play?