I have a 91 accord exr 2.2L. I installed a factory 2into1 front exhaust pipe that comes off the manifold before the cat. The original flex section had a small hole which was getting worse. It actually sounded pretty kool but my wife didn't like the sound anymore. I also replaced the cat with an aftermarket cat which looked like the original in size. The car ran great before. Now it sounds like the engine is pinging when I drive it. I looked through the honeycomb in the new cat before the install and it looked ok to me.
Is there too much back pressure now? There's no leaks in the exhaust. Just sounds terrible when I hit the gas or go up a hill. No engine lights have lit up on the dash yet. I've been able to run the tank empty and fill up with good gas, and no improvement.
Any suggestions would be appreciated.
JJR

 

Could be a bad o2 sensor making the car run lean which will cause a ping. Could have been damaged during the instal. Or was bad before the repair. A hole in the former exaust system may have let in extra oxogen which would cause the computer to richen up the fuel mixture. Now that you fixed the leak the out of calibration o2 could be causing the problem.