I just went to another FORUM: MBWorld Discussion Forums
Went to a post that really sounded almost exactly like Sharon and my problem posted by A///MG_Power.
What ended up being the problem was the air cooler pump. What was happening to the guy (and the more I think about it to me too) was that when he drove it cold there was no problem. After driving it for awhile and the car heated up the car would lose power and not respond.
This would follow because unless the technicians are really driving the car for awhile they won't see this problem.
The test was: "Have the Technician check the inlet air temperature after driving hard. If the temp climbs excessively then the intercooler pump is the most likely suspect."