Catalytic converters can go bad and potentially plug the exhaust, hurting engine efficiency and performance.Google+
Car Problem Reports
Ford F-350 Catalytic converters may go bad and plug exhaust
Ford F-350 Problem
Exhaust & Emissions Affected: 7.5L V8
Average Mileage: 85,200 mi (16,000 mi - 211,000 mi)
Visitor, 1990 Ford F-350, 40,000 mi
after driving for a while when turned off very hard to restart
When i hit the gas it sounds like a engine knock really noticeable in 3rd to 5th gear smell of exhaust is strong in the cab and has no power
Visitor, 1993 Ford F-350, 49,000 mi
Bogged down. overheating. very poor performance. Eventually could only get up to 5 miles per hour. disconnected catalytic converter. problem went away. Replaced catalytic converter. works great now.
Visitor, 1992 Ford F-350, 110,000 mi
Cat plugged. Engine died and would not run. Loosened the exhaust to drive to muffler shop. New cat cost an arm and leg because it is a special one. Haven't had the problem since.