I have a custom Magnaflow exhaust. The 2 secondary cats were removed, the piping is 2.5" all the way with an x-pipe.

When I am slowing down and coming to a stop, sometimes you can hear/feel a popping sound from the exhaust. It only pop's one time, but it does it almost every time I am coming to a stop.

 

No ones gong to try anything so I will. I think when you slow down the a/f goes rich. That hits the first cat and causes a backfire, like in some race cars when the fire shoots out the exhaust, but you have a cat and the exhaust tubing is too long so you can't see it. The secondary cat acted as a kind of muffler, your exhaust still has a "rich" spike but you can't hear it becaust of the cat, and I guess since since its a cat it could catalyze the gas charge thats left.

 

So basically, it's caused by the car running rich when I'm slowing down? Anything I should be worried about?

 

I don't think so. If you check the vid of the LMS no cat exhaust it really does it. Maybe Lobux will check in sometime and give us his thoughts.