2019 international lt625 def delete

[Rare22]

After purchasing a deleted truck it ran perfect when it was bobtail but once I put a load on it. It had a code pop up SCR 25% derate. I asked the seller who go me in contact with the tuner and said it fine likely due to low coolant or anything else so it will show that code. I did indeed have low coolant once I topped it up (it was leaking from a loose clamp) the code never went away. And the mpg are horrible. While loaded with 8k lbs I get 5.5mpg!!!! I see that the truck has great power from 1-10 speed but at 11th and 12th gear since it’s an automatic the truck is very sluggish! I noticed it had a boost leak and I’m chasing them down when I fix a boost leak I would get good mpg for 30mins then it would go back down. Do you guys think I have more boost leaks to chase down or possible a bad tune? Thank you!