If the exhaust manifold is turning cherry red, this indicates that the ignition timming may be too retarded, or the cam timing is off. Have you attempted to set the timming?

-Rip

Is this trully an '86 200 SX, if so I do not have the procedures with me, I can send them tommorw when i'm back at the shop. However, under the hood there is a lable with the timming specifications and procedures (unless the lable was removed). Basically you disconnect any vacumme lines at the distributor and loosen the distributor hold down bolt slightly. You turn the distributor slightly clockwise or counterclockwise in the direction that makes the idle raise slightly-this is the direction of advance. You will also need a timming light (available at most part suppliers). There will be marks on the front crank pulley and timming cover. The timming light is used to check the relation of the mark on the pulley to the mark on the front cover, if they are close you can adjust by turning the distributor. Once you get the timming set if the engine still isn't running properly you may have deeper issues, possibly with the cam timming. When either timming is incorrect, unburnt fuel leaves the combustion chamber and ignites in the exhaust manifold, heating up the manifold red-hot.

-Rip