I am planning on replacing my stock exhaust (pipes and muffler behind cat converter) with a borla or magnaflow system. I am wondering if there is any reason to replace the catalytic converter and pipes that run to the headers for any reason? Is there any advantage or just because they have surface rust, does that mean they won't last for awhile still? It is a 5.9 2002. Thanks.

 

They are stainless on the inside and will never rust out, just the coating is showing rust. You may want to get some performance headers though if you plan on modding your D.

 

Your stock right now right? If you are than you don’t have headers you have an exhaust manifold, probably the rusted part which you are referring to, that leads to the catalytic converter. If you really want the most exhaust performance, replace the exhaust manifold with Stainless steel headers, install a 3”high flow catalytic converter, exiting to 3” muffler and pipes. But that is a lot of work with cutting, fitting and welding. To much work for me since don’t have the time space or all the equipment to do it all. I did the $500 borla cat back install in 3 hours. It increases your exhaust from the 2.5” from the cat to 3” inlet on the muffler to a 4”exhaust tip. All you need is a sawzall and some sockets. Cut off the old exhaust just after the cat union, fit and tighten the new one. I have 140K plus miles on the borla and the system is as good as new, but the tip was polished steel and rusted after two years. The muffler and pipes are still spotless. Replaced the tip (mostly for show) and good as new. Horse power increase seemed minimal in the beginning until I installed the cold air intake then it was really noticeable. If you don’t have the money to do both upgrades at the same time do the exhaust first because if you do the intake first you might clog your cat because the stock system can’t handle the added flow.

 

Thanks. I think I am going to just go with the cat back system (magnaflow) for now. That will be a good start. Just got the 2002 5.9 a few months ago and it just passed 50,000 miles.