05 Pacifica 3.5L surging at 35mph

When I am traveling at between 30 and 40 mph and I am steady on the gas to hold speed, the rpm's fluxuate a little and the transmittion feels like it is right on the edge of shifting. Basically the vehical gets a surge of power and lets off, surge and let off, once I either get on or off the throttle it stops. If I stay in that mode for a bit it gets more severe and it kicks a little harder. It does this every time and is very easy to reproduce. If I put the tranny in autostick mode it seems to go away for the most part. It also stalled on me while in traffic trying to get up a parking ramp. No codes tripped. I thougth maybe throttle position sensor had a bad spot but I figured that would trip a code. Any ideas? Anything I can try to narrow it down? Fluids are all good and I maintain it very well but my wife drives it so who really knows. Fouled plug? plugged injector? any advise will help.

Hey...
Mine does it too! Mostly when cold, but also after it's been driven at highway speeds for more than an hour, when I get off the highway, it will do this smae thing again.
It does go away when in autostick mode, but my wife gives me that "you're gonna break my car" look when I put it in autostick... so I just deal with the bobble at 35mph.
There was a recall for the gas tank sensor, and an ecm flash years ago that "kind of" improved the symptom and shifting bobble, but by now, you should have had that fixed on yours.... but..again...it still does it, just not quite as noticeable as it was when it was brand new.

We love our PAC. Sucks that they stopped making it.. the Journey is too small.