2002 Chrysler Town and Country Engine Stalls

My daughter (with 4 kids under the age of 6) owns a '02 T & C which has started randomly stalling out, actually over the past year. This normally, but not always, occurs while the engine is cold. The van has been in the shop numerous times with the standard diagnosis of "cannot duplicate symptoms." She's spent nearly $800 on these useless shop visits. Her brother-in-law has replaced the coil pack 3 times. Each time the car runs well for several weeks and then reverts back to the stalling condition. I haven't heard whether the removed coils were found to be bad. One point of interest (at least to me) is that the stalling seems to always occur when she has the vehicle in drive and at the brief point between braking and then going to hit the gas. After a thorough interrogation, she revealed that during that brief moment between braking and acceleration, she can watch the tach drop to 250 rpm and stall. The only engine process (at least that I can think of) involved in the transition from braking to acceleration is engine vacuum. What do you think? I'm willing to do whatever I can to help my daughter's family. This is an unsafe situation and my wife and I are contemplating giving her our '07 Sienna.

Any help and recommendations would be greatly appreciated.

Richard