This relates to a 2003 Z06 that someone just bought from a dealer a few weeks back.
The last owner had some wacko grind CAM, head work, headers and who knows what else and then new owner added one of those POS Vararams.
What is clear either the past owner to sell the car and/or the dealer to make the car meet EPA smog the new owner ends up with :
1. Dealer having to install rear 02 sensors that were missing
2. Clearly car had headers and were taken off and in place they installed not LS6 BUT LS1 exhaust manifolds and new stock catback system.
3. Dealer blewout whatever tune the past owner had done. With the mods the engine would not run with stock GM tune so owner had a tuner done that tuned over all the faults and still engine ran poorly
Z06 ran like total crap, this was the first Corvette for the new owner and had no idea of what happens to these cars when hacked on in most cases crap mods that end result is past owners selling car just to get away from the mess.
We found in testing and OBD scanner data collection that the fuel trims at idle pegged at 25% too lean for both heads, and engine wanting to die on decel and coming to a stop.
Front 02 sensors reporting way lean, far less then the normal EPA 14.7 AFR ( .450 mVolts.
In asking the new owner and teammate Dennis to trace out the EPA smog AIR system they found the smog pump missing, the vacuum hose to control it uncapped and worse is someone to fool smog stations they installed the AIR hoses to both exhaust manifolds but the 2 ends of those hoses were not connected to each other at all and one of the AIR check valves missing.
This meant air was always being pulled into the exhaust manifolds causing the O2 sensors to see maximum lean conditions which then the PCM would be commanding excess fuel injector ON times.
Add to the problems the exhaust manifolds are for a LS1 not a LS6 which has a good chance the wrong gaskets were used adding to air/exhaust leaks
So we have a past owner screwing up the car, dumps it to a dealer for another car and then dealer has to do whatever to make the car smog legal again and in the end the new owner unknown to him has bought a basket case for their first every owned Corvette.