About a year ago I installed OBX long tubes and MAgnaflow mufflers. I also put a C&L intake on it with a Brenspeed tune. The OBX came with an offroad Hpipe so I used that for a while, but then later, had a muffler shop weld in some Magnaflow hi flow cats so I could be more street legal here in PA. Well the first set of cats lasted about 2 weeks. One failed and started rattling, then about a week later the other did the same. The muffler shop changed them out no charge. In the meantime, the exhaust at times, over bumps with make contact with the underside of the car, usually at the back. Back to the muffler shop...They pushed some stuff around and retightened it and it would be fine. Then I'd hit another bump and from then on out the exhaust would clank around. Now a year later and maybe 5000 miles later, I hear the cat or cats rattling again. I don't get it. At first I thought it was my Brenspeed tune that was overheating the cats, but now I'm wondering if it's the clanking around that's killing the cats. Any ideas? It's stressing me out to the point I don't even want to drive the car. Also, this muffler shop is supposedly the best in the area, yet they could never make the pipes stay put.

Mike

 

I'm running high flow SLP cats with an SLP X-pipe. Even with the supercharger, I've had no issues with the cats, and I'm running a fairly rich, conservative, daily driver tune. Maybe you need to buy a different brand of cat and/or a different muffler shop?