Nissan Repair: Exhaust manifold glowing orange, exaust manifold, cab 4x4

Question
Hi I have recently purchased a 1994 Nissan Reg.cab 4X4 PU w/ a KA24E engine 2.4 litre. The exaust manifold Glows orange when running @ high speeds. My altenator has recently failed and been replaced w/ new.  It still is doing it. I thought it might be a blockage in the catalitic converter but found someone beat me to it and cleaned the inside out completely.  Would it be an emmissin systems problem or something else. The Oxygen sensor has also been replaced. this is the area I noticed was red hot. Thank You.

Answer
Rob,

I had a Corvette do this once and it was the alternator.  The voltage was so low the injectors were starving the engine and resulted in a glowing manifold.  If yours is still doing it I would check the alternator to see if the voltage is 14 volts and if not I would replace the one you have installed.  If the alternator is good then I would be checking the injectors to see that there is enough pressure feeding them and they check out ohm wise.