2004 745i new in june 2004- now have 135000 miles. have been getting the "service engine soon" notice, and the dealer read the codes- bad catalytic converters. the cost is about $4800, but the price will be lower as BMW north america will participate. the question is, should the cats burn out at 130000 mi? I always used 93octane, got all service on time at dealer, oil chs q 6000 mi, etc. could the sensors just be bad? how to check? is there a secret warranty on these things? could it be a result of bad seal on that engine air injector that was thesubject of a recall? I planned to keep the vehicle for 10 years, but would hate to plan $4800 every two years for cats.