what to look for when buying a newer truck w/ ISX?

[ScarfaceTrucking]

hello everyone i need some help im thinking of buying a modern truck now that there are some good deals out there and dealers are desperate to sell, i hope you guys can chime in some help.

im looking for a kw or pete with a cummins, i know many are using paccar but i live in the middle of nowhere and no one around here even knows how to work on paccar except the stealerships, so i have to go with cummins.

i been told the cm2250 and cm2350 are "high compression engines"? and they dont like to be turned up which can lead to blown engine, and i should be on the lookout for badly tuned trucks because of this reason is this true?

also should i prioritize a truck with a APU? because from what i understand the emission system and truck in general really suffer from long idle times, so a truck with an APU would be less chance of it being a lemon right?

all these trucks for sale are company trade ins so its a giant gamble but any tips/tricks i can get on what to look for would be welcomed.

thanks to all hope to learn from you guys.