[oldsub86]

It looks like the bolt that holds the two manifolds together is missing. Look at the right side of the photo. There are 2 studs on the exhaust manifold at the back (side next to the engine) that go up through the intake manifold and have nuts on them from the top. There is also a bolt that goes up from the bottom on the front through the exhaust manifold and into the intake manifold. I went through this last summer. The truck started being noisy - exhaust leak. Discovered this bolt was missing and took the manifolds off and separated them. The gasket between was about disintigrated. You don't want to leave it like that as the exhaust will ultimately damage the machined surface between the two manifolds and then you may need a new one. Machining will change the way everything lines up if they have to take much off. Cleaned it up and put it back together with a new bolt and studs. You leave it a bit loose until you have it torqued to the head so that the lineup will be correct. Bolt wouldn't tighten. Had to take it off the truck again and drill out and rethread to a larger bolt size. Touchy as there is just room for the next bigger bolt size. Seems to be ok now. Be careful with the "ears" where the manifolds attach to the head. I broke the front one trying to get it tightened back up. The books advise a torque wrench but about half of the spots won't permit a socket so you have to use a boxend or openend wrench.
As to heat riser itself - I wouldn't tie it open or take it out. The spring or the shaft may be worn. If you take the manifolds apart you can check it out. It serves a purpose and wouldn't be there if it was not required.