It seems as though my high rev/backfiring troubles may be tied to a vacuum leak. When I removed the upper-to-lower plenum gasket there was no kind of sealant or adhesive material present. Should I put anything like that on there? Compression is 120+ in all cyclinders. What could be the cause of such a lack of vacuum? Thanks to all in advance.

 

Don't put sealant on there. Inspect the sealing surfaces carefully for nicks and gouges. Inspect the gaskets for integrity. Replace any that are doubtful. Inspect all the hoses for cracks and hardening.
Inspect the check valve at the brake booster for cracks or leaks. Put a finger over each hose connecrion to check for leaks while the engine is running.
Check the EGR and PCV circuits.
You may be able to find or confirm a vacuum leak by listening through a tube. Put one end of the tube close to your ear and check suspected spots with the other end of the tube.
Spray carb cleaner on a suspected area. If the leak momentarily stops, it's confirmed.
Your upper manifold may be warped and not mating properly with the lower manifold. If you can get hold of a precision straightedge, check the flatness of the mating surfaces.
There's a proper sequence for removing and tightening the bolts. Make sure you follow it properly.

 

O.K., the lack of vacuum seems to have come from the egr tubes to the manifold not being connected properly. But the idle is still at 3800! How exactly do these tubes connect to the manifold? The Haynes manual shows a silicone gasket between the tubes and the plenum. Don't recall them when I took it apart. How do the gaskets attach? Thanks.

 

It might be helpful to take a look at the parts catalogue for your specific vehicle. Go to chryslerparts.net and pull up the parts book for your model and year. Search for the EGR system ant you should find an exploded view of your system. From that you may be able to figure out what goes where.
Sounds like you are getting close to getting it fixed. Let us know how it comes out.

 

Allright, I finally found the source of the vacuum leak. It was missing silicone gaskets that seal the egr tubes in the plenum. Thanks to everyone for their patience with me and their advice and solutions to my troubles!

 

Hooray!!!
How is she running?

 

It was running good but just now it started stalling for no reason. At first it threw a 1294 code but now there are no codes. Going to disconnect the battery and let the computer reset. Hopefully thats it.

 

maybe the pcv is craked