Help needed
 

I currently bought a 95 Chevy with the 4.3 tbi. Since I bought it I have tried to get it running better. I put new distributor cap, rotor, plugs,wires, new map sensor, new engine coolant temp sensor. It doesn't have any vacuum leaks. It will not idle if you have the map sensor electronic connection plugged in. If you unplug it it will idle fine but is very sluggish going down the road. It threw codes 13 and 34 which is O2 and map sensor low voltage since it was unplugged. The guy before me took out the 02 sensor and welded a piece of metal in replacement. The EGR valve is free and not stuck open. I have tried 4 different computers in it so it isn't that. The exhaust seems to not be plugged up as it come out pretty good. Anybody have any ideas? If so plz help

Have you tried replacing your Mass Airflow Sensor?