I have just brought back to life a 1974 2.0 914 that has not run since 1999. It is not running to bad for never having left my garage. It smells on the rich side but the my real question is: when I rev up the engine and then let it decel on its own it almost dies and then come right back to a smooth 900 rpm, how can I get rid of the "almost dies" part? Anciously awaiting any responses.

Not that I know if it really does anything, but is the decel valve installed? I think I've read that the purpose of the decel is to slowly bring the motor back to idle when you let up on the throttle.

Too rich a mix will do that behavior. Check to see if the CHT is in spec, check the MPS to see if it holds a vacuum and doesn't leak and check for vacuum leaks at the hoses, seals, intake gaskets, injector seals etc. Weak vacuum causes the MPS to richen the mix.
At idle reading a vacuum gauge you should have a steady 13-15 hg on the gauge...misadjusted valves can cause weak vacuum too. Did you adjust those correctly?

Djet runs on its vacuum signature, meaning the Air fuel ratio is set by the manifold vacuum using hte MPS which reads the manifold vacuum. 15 lbs hg is at idle so the MPS needs to see that to know the engine is at idle. Ohg is at wide open throttle and full rich as you are accelerating. The vacuum reading at partload or cruise is around 4-5hg so if the vacuum is off so is the Air fuel ratio.
Make sure you have no vacuum leaks! New hoses etc, adjusted valves....

Do you have a copy of pbanders D-jet reference/repair guide?
If not, do a search. You'l find a link to copy it. It has all the technical info you need. Then its just a matter of testing.

is your flywheel stock? has it been lightened?