2000 Saturn L200 engine

My car is a 2000 Saturn ls2. I'm driving down the highway at 55 mph, when the car starts acting like it is in neutral, the gear indicator says it is in 3rd gear. The gauges like the speedometer quits working service lights, security, and fuel gauge come on as well as the battery light. I took the car to a local mechanic shop, they hooked it up to a computer, and said it needed a new throttle body and a ecu or bcu, I paid to have them both replaced, and the car still acts up.