hello, the exhaust system comes in three sections for a 1996 tercel..
the front section.then the catalytic converter.
the middle section,and the
last section which includes the muffler. I have never heard of a single piece exhaust from front to back.
are you sure the mechanic replaced the whole exhaust system including the catalytic converter? maybe the mechanic replaced the whole exhaust system because it was in bad shape. even so they should have let you know what they were going to do to your car and
give you an estimate on how much it will cost you.
good luck resolving this situation.
regards, JOET/CAMRY