So I took my car in the other day cause it had been acting up. The temp gauge is saying it is running hotter than normal, 3/4 of the way up the gauge, however when the shop had it they hooked it up to a diagnostic and it was showing it at 98 degrees Celsius which is around 208 Fahrenheit.

There were some codes that came up. They had said the scanner required the VIN to be input into the computer for it to code the problems and they are:
16518 - O2 Sensor Circ.,Bank1-Sensor1 No Activity Detected
16538 - O2 Sensor Circ.,Bank2-Sensor1 No Activity Detected
17604 - O2 Sensor Heater Circ.,Bank1-Sensor1 Electrical Malfunction
17605 - O2 Sensor Heater Circ.,Bank2-Sensor1 Electrical Malfunction
17606 - O2 Sensor Heater Circ.,Bank1-Sensor2 Electrical Malfunction
17607 - O2 Sensor Heater Circ.,Bank2-Sensor2 Electrical Malfunction
17829 - Sec.Air Inj.Valve Circ Short to Ground
17833 - Tank Vent.Valve Short to Ground
17843 - Sec.Air Inj.Sys.Pump Relay Circ. Short to ground
17880 - EVAP Emission Contr.LDP Circ Short to Ground
17923 - Intake Manifold Changeover Valve circuit Short to Ground

The codes had been erased and then the car driven and the same ones popped back up.

The shop is a little confused where to start with the issue for diagnosing it. I would rather try to avoid the dealer if possible but will if I have to. They were suggesting it may be a faulty computer but don't want to throw one in and not have that be the problem. Any ideas on where to start?

The AC has been acting up as well. It will blow cold for a few minutes then blow warm muggy air.

The car is a A4 2.8 Quattro with a manual transmission.