Two problems related to catalytic convertor have been reported for the 1999 Ford Mustang. The most recently reported issues are listed below.
Vehicle would vibrate severely when driving. Intermittently transmission would not go into gear. Dealer contacted. The dealer could not understand how the transmission had no leaks but was out of transmission fluid. This vehicle has had 2 blown head gaskets, the rear seal in the motor was replaced, the heater core, the transmission, and the catalytic convertor have all been replaced.
Egr system caused buck or skip feeling. Has been in and out of verious dealers since purchase date. Other dealers have experienced same problem with no resolutions. Will provide more details if needed.