On point. Many thanks to everyone. That explains everything. After repairs it would throw a pending p026d, a day or 2 later mil would set 4 miles away cold start coming to stop. I was frustrated yesterday, forced another, second regin since putting together, noticed a little smoke coming from down pipe clamp. I didn’t even have to take it off but first couple hours in the job it looked to be the easiest thing to do on the truck.. After the truck cold down, I refit the down pipe clamp. Mil nor pending code hasn’t come back. I just checked my maf, 15.4gs and O2 1 content, approx 0? I thought the nox where just used for regin? The job was no fun, hope I’m in the clear. Thanks again for clearing up the questions