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Question: Can a PCM be programmed incorrectly, or wrong model yet programmed?

I own a 2001 dodge neon 2.0 SOHC basic
Problem: The engine starts but idles erratically and loops, REVving up and down. This problem started after the PCM was changed due to an oil leak that spilled onto the old one. Before the leak the car ran perfectly with no signs of this problem.
YET, since the PCM was purchased through a non-credible source, via Craigslist, i fear it was not specific to the model of the make.
Also to make matters worse there is not a check engine light nor any codes.
I have changed several sensors in my hopes to fix this including the TPS, IAC, EGR(purge solenoid), PCV, MAP, and i just bought the Crank Position sensor.

My concern is that maybe it is not the sensor but the PCM itself; Maybe it was in fact programmed to a wrong PCM, or a programmer error, mainly just programmed incorrectly.

Last note: I'm not a mechanic but I suspect the PCM also because upon turning the key forward, I hear a loud buzzing in the throttle body near the IAC and TPS, which leads me to believe its the PCM sending an incorrect signal to the IAC that is telling it to move to an invalid position. Still this is just my inexperienced guess.