Error Codes???

I pulled the following codes off my 95 s-10 blazer. The vehicle has 170K on it and I am not willing to put an huge sum of $ into it at this point. I would like to get it through another winter or two if possible but it is not my daily driver.

P0113 IAT Circuit High input
P0138 O2 sensor bank 2 high voltage
P1442 EXAP Vac Switch

Here is what I have done to the truck lately:
1. entire new cheap exhaust from Meineke (possible why the O2 sensor is crapping out....cheap catlytic converter?)
2. New egr valve (cleared up that code)
3. Both O2 sensors are new (Bosch)

The truck has a rough idle on start but seems to go away after driving for a few minutes. I am considering putting installing a new cap, rotor, wires, and plugs to see if that clears anything up.

I really don't have a clue other than that....

Any help would be appreciated.

Thanks in Advance,
Greg