I may know what it is on the old engine the o2 sensors were downstream past the catalytic converters in the xhaust pipe, the new engine came with an exhaust manifold with the o2 sensors right up near the block but i used the old exhaust manifold that has those bungs plugged and the harness to those two o2 sensors near the blocks are still on the engine just not plugged in, but the downstream 02 sensors are connected, could that be the problem
Hard to read this... It sounds like you may have mix of Cali and non Cali emissions parts. Not sure what you are up against if this is so.