In the spring of 2005 I purchased a 1988 740GLE that runs good until both the car and weather get warmed then it run's terrible. It will backfire,buck and have loss of power. I have replaced the cat convertor thinking there was a blockage causing the lack of power I experience when the vehicle is warmed up. Previous owner had also replaced the cat about two years prior to selling the car. I ran the car for the first time this winter and I did not experience the problem at all. As soon as the weather started to get warm the problem started again. I have also replaced plugs,wires,cap,rotor,fuel filter & ignition module. Any idea's would be appreciated,thank you.