After spending over $900.00 since December just for parts, my car seemingly was running smoothly. Now as soon as the engine warms up the car goes nuts. It bucks, dies, and runs like sh__t. Yesterday for the first time I kept the car running by stomping the throttle and hoplding it while it surged until it coughed and died. I opened the hood and discovered smoke coming from the area of the catalytic converter. it sounds like a lot of back pressure has bulit up?