2017 GMC Yukon Denali 6.2

[Kay]

I have a 2017 Yukon with the 6.2 in it.  It needed a new engine due too loss of compression in one cylinder, so had a new GM engine installed its also had new GM injectors, new GM Maf sensor, new GM throttle, new GM spark plugs, new GM coils, new GM Ect  sensor, new GM barometer sensor, one new GM o2 sensor, and a new GM fuel pump.  Truck has a mild squeak while running even when belt is removed. The major part is it is over fueling it blackens the plugs with soot in about 15 miles has a rough idle  especially at start up. Showing misfires on 2 , 3,and 5 at start up. Been to three dealerships hints the reason of all the new parts listed. Still no resolution  here.  Throws p050D and a p0300. Called GM corporate but they say take it too a dealer. Was hoping someone on here could maybe have a suggestion what to check that might be over look.