Engine lowers and I must press accelerator pedal almost to floor so I can pull

After this amount of time it could be something new. An overheating or tired fuel pump will cause a similar issue. Considering the age of the vehicle, best thing would be to get it in to a shop for proper diagnosis. There may be several things wrong but only one contributing to your issue! http://repairpal.com/mercedes-benz-within-10-miles-of-carson-california-90746