X15 efficiency advice

[Nero]

X15 efficiency new here.
Hello all, Rookie OO here, with no mechanical experience. Im learning from people like you on the fly.
2019 KW with X15 Efficiency Series / 12 speed eston endurant, 2.79 rear end... ( after reading yaws post i know its a bad set up.)460K miles with 11020 hrs. My trans is auto shifting up at 1300 down to 980 rpms. I would love to know if could change the settings without doing anything with ehe rear end at this time. I did turn up the rpms from 600 to 710 at idle using insite. I just did a overhead set everything looked good. No soot, smooth rollers. No codes according to insite, but today i took a road test with engine monator on and got this

"The engine torque and/or speed output is being limited by an active fuel system fault".
And
"The engine fueling is being limited due to lack of oxygen (boost pressure). This state will normally be active for a few seconds during a hard acceleration to prevent excessive black smoke. Excessive time operating in this state indicates the lack of boost pressure (oxygen) entering the engine. Troubleshoot the air intake system.

No codes are enginelights.

Thanks for any advice or input.