Hello and welcome to Just Answer. My name is Steve.
I'd just like to ask you a couple of questions first.
How many miles are on the Corvette?
Does the "Service Engine Soon" light come on while driving the vehicle?

Hi Mike
Obviously the car is getting to much fuel when gas mileage drops that much as you may know.
The thing that concerns me is why they changed both O2 sensors.Usually when an O2 reads bad on the scanner there are reasons for it. The O2 itself is usually fine.There are many things that can cause an O2 to read bad.
The symptoms that you have listed usually indicate a coolant sensor,air intake temperature sensor,or bad fuel pressure regulator. If any of those go bad it will cause it will cause to much gas to be injected into the cylinders.When that happens the O2 sensor will read bad on the scanner because the O2 is monitoring the exhaust and trying to compensate for the extra gas.
There could also be a vacuum leak.
The Gm guys should know this. If you get a chance talk to them and ask them what the exact O2 readings were before they changed the sensors.Be sure and tell them that you want to know the exact millivolt reading.
They might not like you asking that question but you're entitled to know that.
Also those readings will help me a lot to help with the diagnosis.

I think the traction control is another issue unless the mechanic bumped something while changing parts which is possible.

Let me know what you find out.

I'm glad to hear that they finally solved your problem and the Corvette is back on the road.
I hope you were satisfied with my service here.
I can't judge a repair shop but I think they should have known things better.

Also if you get a chance please take time to rate my service and feel free to leave feedback.
Most importantly I hope your expirience here was great.