Van sporadically has almost no power; sometimes stalls when stopped

My '98 Dodge Grand Caravan (6 cyl 3.0 L engine) has been occasionally stalling since Feb 2009, and I first noticed power loss on acceleration in April 2009.

Work done Sept 2009: fixed hole in exhaust (one of the manifolds), replaced water pump, replaced timing belt

Work done Spring 2010 (after stalling issue began): fixed 2nd hole in exhaust (other manifold), new catalytic converter, new fuel filter (outside tank only), air idler valve

April 2009: first noticed loss of power on uphill

Work done late Spring 2010 (after stalling and loss of power issues): both O2 sensors replaced, both manifolds resurfaced (due to heat damage) + new gaskets, new thermostat, new EGR valve, complete tune up, new ignition coil.

June 2009: checked transmission & it is OK

None of these repairs has fixed the issues of the stalling & loss of power! We have already spent more than the vehicle is worth on repairs!

I have noticed that the loss of power is much worse on hills and after going uphill. If the van then rests for awhile, it runs OK. The loss of power also happens in reverse if the vehicle has first been pushed too hard on a hill. The engine always has a hot smell when it loses power. I’m starting to think (though I have no empirical evidence) that there’s a connection between the weather and the vehicle’s behavior. On rainy days it seems to be worse than on clear days (though that’s hard to test, living in the Northwest).

Could it be the fuel pump? What should be checked next? Help!

CORRECTION: sorry for the confusion…all dates should read 2010 except September 2009.

SOLUTION: I took this to a mechanic and he found the problem. The flexplate had broken, turned a bit and gotten stuck. That’s all. Now it runs great. Hopefully, this will help someone else with a similar issue. The transmission had to be removed to find the problem.