These are images taken from this C5 after 100 miles on new engine and the lazy and non experienced work by this shop

Notice the rear O2s, they cut the wires off to leave O2s in pipe rather then doing the right thing and keeping them functional but at least if they were not going to use them was to seal the bungs rather then cut the wires which BTW with the cut ends become a EMI/RFI noise path to confuse then PCM

Notice at idle the engine only had 9 PSI oil pressure !
and then the damage in only 100 miles to the main bearings of crank !

Pure and simple, owner paid over $10,000 and got a new engine blown to shit.