I had loose honeycomb in my cat and discovered a good test: Get a rubber mallet and lay under the car (NOT RUNNING!) and thump the cat body with the mallet. If you hear the rattle there is your answer. You can buy an aftermarket cat here for a lot less than you were quoted, call Phil.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra