they checked the coil, said it was fine.

The same thing happened again this morning. I start the car and need to drive about 10 blocks to get on to the highway enterance (alls fine). I ALWAYS catch the same light right before I enter the highway, when the light changes it then starts to happen the car struggles to reach 50mph when I'm entering the highway and when it does reach 50mph it then starts to lose power. (I think I'm going up hill). Then drops to about 20-30mph and I have the pedal to the metal. This continues for about 1-2 miles then it starts to pickup, then it's fine for the rest of the highway ride.