The MAP sensor bolts directly to the intake with a tiny L-shaped rubber elbow, tried one off my wife's G-Cherokee.(no difference) Elbow is solid, not deteriorated.
Exhaust system is tight, new manifold, cat, muffler,tailpipe only the headpipe is original. I did have several leaks with the original cracked manifold but not sure if I had the problem at that time, thought the TB was gummed up.
Ran a road test with a professional vacuum gauge, seemed pretty normal, 16.5" idle, 22" under decel and near zero under WOT.
Here's the real kicker, two days ago, took a 60 mile trip (in the rain) and it appeared to be almost normal dropping to 750 rpm's when completely stopped, as long as it was moving it would only drop to about 1000-1100.
(maybe the PCM is programmed that way?)
Today the problem returned, dropping to 1500-1600 (clutch depressed) but still rolling, once completely stopped it drops to 1000-1200.
I'm going to take a look at the speed sensor and any possible connections going to the PCM.