For the fuel trims, did you replace the big O-ring that goes around the PCV valve when you replaced the upper intake manifold? That will act like a vacuum leak.
Also, make sure the plug wire to #6 cylinder is taut and away from the oxygen sensor. It will throw off the readings.
Also, make sure the plug wire to #6 cylinder is taut and away from the oxygen sensor. It will throw off the readings.
