Sounds like a clogged fuel filter, car tops out at 60 MPH and runs like it has a governer on the engine. The more you push the gas, the slower it goes. It's starving for fuel if this is your problem. It's under the car near the fuel tank and doesn't cost a lot. I had one replaced at the BMW dealer north of Seattle a couple of years ago. I think I paid $50 and they did it while I waited, since I was traveling. Excellent Service. It's a job I would definitely have a dealer or shop do, since I hate laying on my back for certain things.