1991 Corolla dies when MAP unplugged

I have a 1991 Corolla with a 1.6 motor(6 vin code). The car is showing error codes 25,26.31 Codes 25 and 26 are for opposite conditions(lean and rich). Anyway as part of testing,I unplugged the MAP sensor and the car died immediately. The car should still run with the sensor unplugged,so I'm not sure what this means. Something else has to be malfunctioning to cause it to die. TPS,ECM,low vacuum? Vacuum reads 18-19 range. Should be ok.The car has been running rough at idle and the check engine light has been on for a while,so I decided to try and isolate the problem.
When getting the codes from the flashing check engine light.... I've read it will flash three times in a row for each code-then go to the next code. Mine did not do this. It flashed 25 pause 26 pause 31 pause 25 pause 26 pause 31...and so on. NOT 25 pause 25 pause 25 pause 26 pause 26 pause 26 pause 31 pause 31 pause 31 and so on. I point this out in case this could be a problem with the ecm. Thanks for any help

Check for a stuck or clogged EGR valve, PCV valve, and/or IAC valve. Any or all of these can contribute to rough idling, stalling, and poor performance. Good luck!