I have had the same problem, once though and it only stalled once, not multiple times after that. Don't know what the problem is but it hasnt happened since. I replaced the Crank Sensor and I'm looking to replace the RCM but that has nothing to do with what you are explaining I believe. It might be a vacuum leak as tighed1 said. Although there is a mechanical diagnosis called Engine Hesitation which occurs when the engine misfires, chokes or lacks power when you are stepping on the gas/throttle. I read a lot of places that it is due to an unideal fuel mixture, too lean or too rich, or something is wrong with the ignition, or the air flow sensor takes into account the wrong amount of air thus mixing in the wrong amount of fuel which in turn can cause a misfire or produce a hesitation when you step on the gas...

-Sam