I drive a 2001 Mazda Protege, 91k miles. I've had it over a year without any problems. I always have regular maintenance done. It should be known that between work and school I commute a lot - about 450 miles a week. About a month ago, my car began accelerating and decelerating randomly, with sporadic shifts. I got the solenoid replaced. It drove fine for two weeks, then I was towed off the interstate because my catalytic converter was malfunctioning (limited air flow). Now, my car will forcefully shift into first unless the engine is warm, will continue randomly slipping at highway speeds (70 mph- downshift- 55 or 60 mph), and will occasionally sputter and die at red lights. Is this a tranny problem, or could it possibly be faulty spark plugs or plug wires? Or could it be an entirely different problem altogether? I'm not able to throw any more money into this piece if it's not going to work.