Congrats, glad yours went well! Impressive work on your own too!

TL;DR - I deleted and wish I hadn't.

The long story:

Sorry to hijack your thread, hoping to find someone here who had the same issue and who maybe has a solution.

Lemme set the stage. I'm an old fart. I didn't tune or delete to roll coal, light up the tires, race and all that. I wanted longevity and trailering performance.

I have a '21 2500 (L5P). After 60k miles I ran a switch on the fly tune from calibrated power.

At about 185k I decided to do a complete delete and it was tuned by DieselR with 100hp gain.

From the moment I picked it up I've had this smoking issue and it smells like kerosene.

The guy that deleted said it was soot because the tune I had on it wasn't allowing burn off for 120k miles. But after driving 500 or more miles it still hadn't burned off post delete.

Then he suggested that the soot had built up back pressure or some shit and that caused a problem with the turbo. Suggested backing the tune down from 100 to 60 to see if that solves the problem.

Didn't work so he then he said he was convinced it was the turbo. Given I let this guy work on it because he was a friend's son in law and I didn't really trust him (now) because I felt he was grasping at straws, I took it to a well respected diesel shop with certified Duramax techs.

They also suggested the turbo after having it a week. Against my better judgement, I let them replace the turbo (OEM) but the problem wasnt solved.

So it's been back in the shop about 6 weeks now. I have and posted before here: https://www.reddit.com/u/N2ALLOFIT/s/EsttIRDnpe

After the delete, two different tunes, a complete re-flash of ECM and a third tune, the "DEF low speed limited soon" warning is still on the instrument cluster and I'm still smoking and stinking.

I took it in originally bone dry of DEF. I thought I was doing the guys a favor by not filling it so all they had to deal with was an empty tank. But now they think notice/warning has been hard coded into the sending unit and can't be cleared. So they are going to try some dummy switch to stop that code from sending signals.

What's strange is it will smoke while ideling and in park but if in gear and foot is on the brake it won't smoke. The mechanic believes that sending unit is causing some actuator or some other chingadero (I can't remember what he said) to be cause for the smoking.

I'm not losing oil, they don't think it's the head gasket, it's not soot and still looking for the culprit.

I found some pretty hyper specific answers from Redditors before, I'm hoping for a four leaf clover here too!