Car not running well? Check for this.
 

I have a 1993 LT1 T/A that I have owned almost continuously since 1996. The car only has 62k miles on it. It is a M6 car that always got 26-27 mpg on the Hwy and had good performance. I haven’t driven the car much in the last 10 years but the performance and mileage had really gone downhill. Since I have had a rattling noise coming from under the car for a while, I decided to investigate. My first thought was that a baffle in the muffler had let go. I bought a cat back system but had not installed it yet. I finally put the car up on my lift with it running. Noise seemed to come from the cat more than the muffler. I removed the intermediate pipe from the back of the cat and found that the ceramic block in the cat was broken. Had to be my problem. Ordered a new Magnaflow direct fit cat/Y pipe and installed. Car didn’t seem to run any better and the noise was still there. Today I removed the original exhaust behind the cat. Multiple chunks of the cat substrate fell out and one large piece was wedged in the inlet of the muffler. I am guessing I had at least 75% blockage in the exhaust. 😳

If your car runs poorly,is getting poor fuel economy and you have a rattling noise, you probably have the same problem!

The first pic shows the piece wedged in the inlet of the muffler. The second picture shows the chunks of converter that were in the exhaust. The piece on the bottom is the one that was wedged into the muffler inlet. I can’t wait to drive it after the new exhaust is on. Will probably feel like it gained 100 horsepower!