2004 Freestar just started hesitating and it would not get over 30 mph.

2004 Freestar-In Jan. it just started hesitating and it would not get over 30 mph. I had it towed to the dealer and they could not find problem. I picked it up and it ran good. I noticed the radiohad lost power and reset, so I got it's first new battery. Now here in March, the same hesitation and low mph, but this time, the engine light came on, it died and I smelled sulphur. It restarted no problem, hesitated and would not get over 30 mph, but it snapped out of it after driving 1/2 mile. The dealer said my altenator was intermittantly going out. I had it in a week before that because the engine hesitated slightly before the engine light and they said the engine light sensor on the catalytic converter was out. I did not have them fix this sensor.

Take van to reputable Ford dealer and have them hook it up to computer and check for any codes.
The vehicle computer might have to be reset for the egr system.What they did was disconnect your battery for the quicki reset for vehicle, thats why your radio had reset