Hopefully we can use this to help new guys learn about the black voodoo that is the dreaded DPF.... Part 1. Background info:
The DPF, or "Diesel Particulate Filter" is a separate canister that is found on the "LMM" or 2007.5 and up Duramax equipped trucks. Here is the wikipedia page on them, it's a good overview on them.
They are government mandated, and are required to be on the truck to be street legal. You'll notice that your new LMM or LML, doesn't Smoke... No matter how hard you stand on the pedal, you can't get any smoke out of the truck? The DPF traps that soot, and over time, will get full of soot, the truck sees this, and sends the truck into Regen Mode.
Here is what it your exhaust system looks like. FYI a DOC is a "Diesel Oxydation Catalyst (think a Catalytic Converter for Diesel)
There are two steel tubes that are part of it as well, they sense how much soot is in the DPF, and if the DPF gets full of soot, then your truck goes in to "Regen" (regeneration) mode. When the truck goes into Regen mode, you may, or may not notice. You might notice any of the following symptoms: a slightly higher idle, an odd smell, reduced fuel mileage, among the most common.
People also say that since the DPF requires more fuel to burn off the soot, that removing the system will net you better gas mileage.
You'll notice that your exhaust tip looks different as well. This is because of the higher temperatures that the exhaust sees while the truck is in Regen mode.
There is a "cuff" that allows outside air to cool off the exhaust tip, just as a safety measure so no one gets burned.
If you get a new exhaust system, you won't have this problem anymore, and can use any tip you like.
Part 2. Removing it.
Now that you've learned all about the DPF, and you've decided to remove it from your truck, here's what you'll need to do.
Do Not, in anyway buy a "DPF Back" exhaust system. It will do nothing
for you.. and it's a complete waste of time.
You will need a "tuner/programmer" that will be loaded into the truck, and will "delete" the DPF system from the engine. These are all sold as "for off road use only". And most tuners require you to register the unit, and sign a release saying that you understand that.
You will need to physically remove the DPF from the truck There are a couple ways to do this. You can either get a "DPF delete pipe" that only replaces the DPF, and keeps all the sensors plugged in. This option is the most costly, but does retain the most "stock" look.
You can also just get any exhaust system you want for a 2001 to 2010 Duramax (they're all the same). You just have to make sure you order what you have, Single Cab, Crew Cab, 6' bed, or 8' Bed.
There are many supporting vendors here that can recommend and sell you the appropriate products to fit your budget.
If you choose to pull the stock exhaust out, you will need to unplug the sensors that go from the exhaust back to the wiring. Just tape up the ends of the sensors, and zip tie them up out of the way.
That's basically it, it's not really hard to do, and it really doesn't take that much time, expect to spend an afternoon in the driveway. Having a buddy to help align up the exhaust will be of great help too. Part 3. The downside.
Removing the DPF from your truck is illegal. There's no way around that. Does anyone care? Probably not. Just understand that someone, somewhere might care. If you live in an area with Smog/Emissions inspections, be aware... you might not pass if this is removed. (again, it depends on where you live, other forum members might be able to advise of Johnny Law's aversion to these in your area)
There are no adverse effects on the truck to removing the DPF. If you have a tuner/programmer that will delete it, you will not having any check engine lights because of doing this.
Removing the DPF from your truck, and the associated Tuner that you will have to put on the truck, MAY
void your warranty. There are many factors that play into this, some are; how cool your dealer is, what exactly is wrong with your truck, how you approach the dealer about the problem, etc.
This is meant to be a broad overview of the DPF for new guys to learn about the DPF.
4. What to do if you've already bought stuff, and now you want to delete the DPF.
If you've bought tuning that will not delete the DPF, the only option you have it to try and sell it.
DPF back (which is really what LMM "Cat Back" exhausts are called) Exhausts... just bite the bullet and throw them away. Or, try to sell them to an unsuspecting n00b. (remember, that was you not too long ago.