That's what my Autel Maxi Sys tells me, when revving the truck the STFT goes to 1 - (-1) and LTFT -5 - (-11) and then they slowly return to the -30's

 

How old/what brand are your O2 sensors???

 

Upstream O2 NTK less than 1.5 months
Downstream O2 NTK 9 Months

 

Hhhhhmmmm..... Were you having the same problem before changing them? Did the problem change at all when you replaced the upstream?

It's pulling a lot of fuel, and I wouldn't be surprised if the backfiring was due to running too lean....

 

Yes, I've been having the backfiring issue for a while

 

Have you tested your cat? I could see it restricting flow the hotter it gets.....

 

Catalytic Converter is hollow

 

Probably not plugged up then eh?

Can you do data logging? I would love to see what the various sensor do at steady-state cruise for 10 minutes or so.... preferably from standing/slow start.

 

The Autel is updating and I have no idea how long this will take, as soon as it's up and running again I'll get that drive logged. I've also gotta change the control arms before I can drive it to the alignment place, but it should not be a problem!

 

Famous last words.