GMC Sierra Denali Questions

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Engine oil flowing out up around radiator steering box area. More when running. Then dumps when shut off engine . Then stops dripping out
I have no idea where it come from or how to prevent it.
There's no heater blowing in the truck. When u turn on the knob no heat but there is sound but no heat comes out
For past few days I observed that the truck dropped its rpm by 500 and idling at 500 onl;y even at 80 miles/hr the rpm suppose to be 2200 but its running with 1700 and the vehicle feel some grinding noise from the bottom, vechile feels rough not smooth.
only happens on cool mornings after its warmed up runs great says "engine power is reduced" and "service theft deterrent system"
Pressed acceleration peddle and vehicle sputtered as if it wanted to die. I then pulled over and shut vehicle off. Attempted to start and it would not crank unless I pressed the gas peddle.

What could this be
I'm looking for rear brake calipers but most online stores just list Sierra Denali. However, I have a quadrasteer and it needs different part from 2 wheel steer. I ordered calipers but thye didn't fit. Couls somebody recommend correct rear calipers for my vehicle. Really appreciate any help. Thank you.
When I adjust radio volume down, it goes up. When I change stations up it changes station down the dail.
This problems occurs about 50% of the time when I'm driving.
I usually just use the manual controls on the radio, they work fine.
Not sure which Denali I have Just says Denali on door. But I bought it used a month ago love it so far, But experienced a problem just before Christmas with auto lights, put vehicle in drive and head lights did not come on after messing with switch for few minutes then started working. Now if you go to bright and back sometimes the lights go out. But if you place back in bright come back on. What can I do to repair this I really like my Denali.
Sounds like slack in the DT somewhere. Notice it leaving a stop (not always.) S. Denali is a 1/2 ton PU. 5.7/6.2 litre.
any help would be great

When I start it in the morning it holds for awhile then it start with some black smoke from the back and when the check engine light is on the car can't be start from remote control
Initial symptom was a shaking during stop light idle, took it the dealer and they replace all the spark plugs and found 1 (cylinder 1) with the white ceramic portion broken.
The issue returned a few months later and they found a different cylinder (cylinder 4) spark plug with broken seal, got replaced.
2 months later it started again, and found 2 broken (cylinders 1 and 6). I got all spark plugs replaced but the shaking came the next day!!!
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