why does the pipe that comes off the exhaust manifold get red?

since the last few that answered are on another planet its prob turning red because your cat converter is plugged up. that is a key sign. when its plugged up your front exhaust pipe as its called that goes from the manifold to the converter will glow red.

I have had that same problem and the cat converter was bad and fell apart on the inside and caused it to glow. you cant drive it that way, it has to go to the exhaust shop for a new cat converter. or to the car lot and trade it for a jeep with a bad fender.

Your converter is clogged and most of the time that happens because your EGR valve got clogged witch also will clogge your intake manifold.

The cat. converter is stopped up, bypass it with flex pipe. That should do it. Good Luck..

Yes, I would also say your Cat. Converter is plugged.

Heat makes metal turn red.

also check your antifreeze it might be low and cause this problem

it doesnt