Don't have a ton of experience on these Dodges myself. Although I've had mine for years, it hasn't given me much trouble. So, bear with me. But, I've had similar experiences with other cars.
Sounds like an obvious fuel/air problem. Not sure exactly which parts these vans have on them, but I'd start with suspecting a MAP problem (but you've changed that), a dirty throttle body, a bad throttle position sensor (if these vans have them) and a clogged or bad idle air control valve (or whatever similar things these vans have).
I'm working from what my 3.8 looks like, so your 3.3 might be a little different. But, I'd start by checking to make sure the breather hose is firmly attached to the throttle body. A leak there could mimic a MAP failure as extra air could be coming in after the MAP and reaching the engine without being measured by the MAP. Next, I'd remove the breather hose and clean the throttle body thoroughly with cleaner and a toothbrush. Pay special attention to where the butterfly meets the sides of the body and the butterfly pivot points to make sure it is able to close all the way and to open and close smoothly. (*** Also, make sure you use an electronics safe throttle body cleaner. Regular old carb cleaner can mess up electronics. ***)
Then, I see two electronic components on the back of my throttle body: one at the top and one at the bottom. One is likely the TPS (or something similar) and the other an IACV (or something similar). I'm not sure how to test these on a Dodge, but you could start by removing the connectors, examining the wires closely, cleaning the contacts with electronics cleaner, and then reattaching.
From the looks of mine, I'd guess the lower one is the IACV. Either way, if one is an IACV, then it will have a small port that runs into the throttle body. It will look like a little hole inside there somewhere. When you're cleaning the throttle body, make sure you don't wash extra trash down into it to clog it up, and if it looks clogged or dirty, clean it as best you can.
If the problems you are describing were happening on one of my old Jags, then those things would fix it 90% of the time. Good luck.