OK so here we go. I was told by several garages that my 73 Chrysler 400 engine had a potential wrist pin problem in one of the cylinders and the engine should be rebuilt. It exhibited low speed engine knock and would not idle properly when cold or warm. The engine always sounded like it was grasping for air and the exhaust sounded tinny and smelled rich. I did not want to ruin this engine since it is original to the car and had only 64000 original miles on it. So I found the best shop with great references in the area to do the job over the winter. Was quoted a price between 4500 to 5000 to do the complete job. Well now I have 8300 into the engine and it runs no better than when I took it in. The knock is gone but it still idles rough when cold It will quit once in a while and if run for a period of time have a tough time restarting. Replaced the carb,distributor, coil, voltage regulator, ballist resistor, just about everything you could think of and the car still runs terrible. I am at the end of my rope with this and broke to boot. I thought this would solve my problem and it has only added to it. The carb has been tweeked and adjusted and am told it is working properly by the shop. We are at an end to finding a solution. Do any of you have suggestions as to what it might be? Any help would be greatly appreciated.Also the exhaust still sounds tinny but the rich smell is gone. It has a new nos muffler on it and sounded fine before this problem started. Help!