Exhaust manifold gets Red HOT!

I have a 1986 GMC VANDURA 3500 with a 350 v8. One side of the exhaust manifold gets red hot after 3 minutes of running. It appears that side of the exhaust has a valve that has a hose that runs to the front side of the carb. It appears that the valve is suppose to open to allow the exhaust fumes to exit the tail pipe. I do not know what they call this valve and the auto parts house has no idea either. The engine is in a motorhome and it looks like it has chrome risers that connect to black boxes and hoses that run to an air pump of some kind. Since the vehicle no longer has to pass emmissions testing could I remove the valve and would this fix my problem? any help on this would be appreciated. The engine was just tuned up and I have eliminated timing and carb issues as the problem.:banghead:

The part is called a heat riser valve, it's an emissions device, and they are common to fail on older vehicles due to corrosion (low mileage) or carbon buildup (high mileage).