Okay so last Wednesday I was going down a bridge and was going pretty fast. When I was in 3rd my car staked a couple of times and what I did was change the gear to 4. After that day it got worse. In every gear the car shakes. From 1,500 to 2,000 the car shakes. After 2,000 the car drives normal. I smelled gas under the hood and I found that one of the fuel lines had a leak. Lucky my friends help change that tube and it wasn't leaking gas anymore. The next day the car still shaked. One time I heard 2 loud pops from the engine and a friend said it was back firing. I don't know whats the problem. I have a 1987 325e e30. Thank you for helping!