Pontiac Repair: Car turns off when its idle, vacuum leaks, pontiac firebird

Question
My car is a 1991 Pontiac Firebird and it is a 3.1 liter. Recently i changed the thermostat and in order to get to it i had to remove the top part of the intake manifold and remove the throttle body to get to it. at first i ran it without the thermostat and the motor decided to shake at idle and finally turn off. so i replaced the thermostat. it still did the same thing when it went into idle. i took it to get a diagonostic run and they told me that the map sensor wasnt working proper, the oxygen sensor and the iac. after i told them what i did they told me to replace the manifold gasket, i did, and i replaced the TPS sensor, and it still did the same thing, so i did some investigation work on it myself and disconnected some of the sensors and when i disconnected the tps sensor the engine reves up to about 2500 rpm, but when i reconnect the sensor to the ecm, the engine shakes and turns off. i think i may have messed up IAC valve position. am i correct or can it be something else..and if this is true what do you recommend that i do ...thank you for your time  

Answer
The IAC is an electric motor that opens and closes an air passage, so it is really an electricaly controled vacuum leak. Too much of a leak causes a high idle and too little of a leak causes rough idle and stalling. How do you think that you "messed up the IAC valve position"? Why did you replace the TPS?
The first thing that I would do is disconnect the battery for about 30 seconds. Then start it up and see how it runs.
If it still runs rough at an idle, check for vacuum leaks around the intake. There may be a hose that came off when you pulled the intake the first time. If you cant find any leaks, I would suggest taking it in to the dealer to have it properly diagnosed.