Chrysler Repair: Short of dealership, wd 40, spring tension

Question
Roland I hope your holidays were great now I want the rest of mine to be great. Here is a description of a problem that driving me battie with my 1993 Shadow 3.0 V6 since I have replaced the heads. The problem is on deceleration (sometimes) the rpm (tach) will drop real low then return to around 6-700. Sometimes it will stall and sometimes not.It used to stall on a complete stop. Here is all that I have done to this vehicle. I have replaced rotor and cap, plugs, wires,tps,ais,and 02 sensors. On a complete stop the tach rpm will always drop down.
I have had it scanned also (with only the ignition key on) and the scanner read no errors? I'm short of going to dealership. Thanks  

Answer
Hi Ron,
Thanks for the good wishes, now to help you have a good balance of the holidays.
There are lots of things that aren't sensed by the PCM:
Secondary ignition system (coil is about the only thing you haven't considered and replaced yet)
The indexing of the timing marks so in light of your recent repair I would remove the covers and check that, and the timing of the spark as well.
Fuel pressure or faulty injector
PCM grounds
Throttle body air flow (air cleaner, cruddy throttle body butterfly or throat)
Cylinder compression (just to prove that your head work was up to snuff)
Oil fouling the plugs (deceleration sucks hard)
Evaporative purge canister being clogged or loaded
Vacuum assisted devices or lines leaking
That is quite a list I know, but it is worth considering before throwing more parts at it. A system that is monitored but may not be so bad as to set a code is the egr valve (if your '93 has one). Check that the valve stem is moving freely back to the closed position by inserting a scredriver into the slot and prying it open and let it close under spring tension. Put a spray of WD-40 on the stem where it enter the valve body. I partially ajar valve will ruin your idle.
I wish the list wasn't so long but that is the fact of life.
Let me know when you correct the problem, which I am sure that you will do.
Roland
P.S. When/if you write back, instead of sending a follow-up question please instead cut and paste this initial exchange in the body of the text of a new question, but this time give the subject as "stumble upon deceleration, low idle speed" or something such as that. Others scanning the list of questions would then be able to identify our erudite exchange!