[12Ounce]

You are asking a good question. I don't know.

But the Haynes manual that I have applies to 1995-2000 models. It shows the Intake Manifold Runner Controls (complete with the individual jets) on all 3.8's from '96 on. At least, that's what I think it says.

I think the whole IMRC thing is a bunch of crap, I think the design rationale goes something like this:
...Some engine designer had a concern about the distance there is for the air to travel between the throttle plate and the "other" end of the engine, cyls #1 and #4.... at low rpm..."there might be a lag time" he percieved. So he divided the manifold airstream into halves and put in butterfly valves... so that at relative low rpms (i.e., low manifold air flow) the "time" between the throttle plate and the combustion chamber is reduced (when the butterflys are closed...speeding the air up)! At higher rpm (when the manifold air flow is much higher... no "lag time" problem) the butterflys open allowing full breathing.

Wow! If he had just had another cup of coffee that morning! I believe there are other (PCM program) ways to compensate for the slow air at low rpm.

There must be something I'm missing, I know. Will someone please share it with me!...????