my car losing power! need help!

currently i m driving a 2001 E240, but now everytime i accelarate to 80 miles/h, my car will lose power and speed reduce to 65-70 miles/h. also my auto gear is having problem, each time my gear changes, it will jerk. i consulted many mechanics but none of them could identify the problem. really hope someone can help me. thanks in advance!

im relativly confused, bcuz mercedes never made an E240, they stopped the E240 around 1996

I smell a rat...