Still shipping but will let you know my feelings on it

Have you checked your DDE yet? (Digital Diesel Electronics) to see if your emissions monitors are set to "ready"? Looking into the same exact thing you did but i live in CA...

Update: prior to change, computer indicated city mileage was 18.2, now I'm seeing over 20 MPG.

Plus, still so much fun.

Deletes are great.

A note on cats, I see some people complain about the odor when deleted, and I see others not complain. I think the choice of tune and health of the engine have something to do with it, but at the end of the day it comes down to personal preference.

My wife and I have both spent a lot of time around diesel equipment. Neither of us has any complaints about the occasional diesel odor.



Cats only do much to help odor once they heat up. The motor stinks the worst on a very cold start, which the cat will do nearly nothing to help.


For me the cat wasn't even a consideration. I've seen others say it reduced odor by 50% vs straight pipe.

Hey John, is the soot that thick when you rev? Where did you have it inspected?

You have a point there. My x5d had some injectors issues for a long while and deleting exposed the problem as worse. I was put off how much smell was there despite opting in for DOC to reduce it. Even with hot engine, stopping to let the kids out during school run would get the diesel smell into cabin when door gets open.

I was also surprised that deleting and tuning did not improve efficiency either.

Then, after replacing 2 injectors, the smell is virtually gone. On a hot engine, the smell cannot be detected in normal everyday driving situations.

MPG improved by a couple units vs. stock as well. On last trip to southern Oregon Coast, MPG for the 900 miles was 26.5.

The best improvement of the delete and tune was passing power. Unbelievably effortless passing uphill.

Towing the boat to camp this summer should be much more pleasurable.


There's really no benefit in going catless ("DOC-less"?). While flow restriction concern is basically a well-established myth, benefits of DOC to both people and environment are well-documented. We are talking about reduction of SOFs by 90% and total particulates by 50%. This is stuff that has been linked to lung problems and even cancer.

I think folks who opt to delete should at least consider either opting in for a new DOC or leave DOC portion of the DPF intact (it has been done: DPF mesh is drilled out, leaving DOC functional).

Just my 2 cents.

Don't get much visible soot at all. Blue smoke at cold start, but that's about it.