2012 hyundai genesis

So i had a small shop install a 2014 3.8 into my 2012 3.8 and everytime i clear codes the same 2 codes come back 24/7, the car drives the same no changes but i dont like the CEL on all the time. How do i remove/fix the issue? My driving was the same before i install the engine nothing changed...

So i just had my 3.8 engine replaced last week and ever since then there is this extremely strong smell of coolant i can’t find it leaking below the engine or in the front by radiator. I’m assuming it’s either pressure related and dripping from rear and burning on the exhaust or on the engine...

So story is I bought the car last week, I was on the forum with few people giving me warning but I didn't listen so now I have a problem. There are times when I drive, When I go from a stop to go the engine would rev between 1x and 3x and the car would jerk. like if the car missed a few gears...

I've been in a serious dilemma with choosing which car to buy, my boss says Infiniti due to reliability though I thought the genesis would be more reliable. What are everyone's choices with which car is good with speed, low maintenance and reliability, I'll be putting synthetic oil and premium gas?

Was looking to buy car, whats maintenance like? Is the car worth buying? heard that parts are expensive if anything breaks down.