Help! Exhaust Manifold at O2 sensor is glowing

[GringoEJS]

I just finished replacing my engine on the 89 240SX, and after a test run, I noticed that my exhaust manifold is glowing behind the heat shield near the o2 sensor. I looked under the car and didn't see my cats glowing. Why would the exhaust manifold smoke and glow??? The car seems to hesitate a little until I hit 3500 RPMs where it then really starts running good.
Modified by GringoEJS at 9:45 PM 6/30/2005