I've had my 1988 M3 for about 6 years now. Until recently, it's been doing good. But now when I pull up to stop lights, the engine feels like it wants to die. One time, it didn't even start when I tried to start it up. I'm not too sure what it is. I thought it was the fuel pump, so I had it replaced. But when I picked up my car from the mechanic, I noticed that the engine still stumbles. I believe that this is one of the greatest cars ever made. I don't want to get rid of it, but I've been paying an arm and a leg for maintenance. Could someone please help? Thanks.