88 V-10 Blazer 5.7 engine runs poorly, idles irraticly and dies out when new MAP sensor is plugged in. Unplug MAP vaccum or electrical plug and it runs at least. I have replaced oxygen sensor, EGR valve, temp sensor, thermostat, MAP sensor, distributor module, plugs, wires, cap, rotor. Replaced most sensors except knock and ESC. No codes since replaced MAP sensor and erased MAP code. Still runs poor when engine loaded in gear. Revs up in park. Cylinders all have 125 lbs of compression and replaced throttle body gasket. What's next?

 

Back to basics
Check timing, look for erratic timing.. if it is erratic, check distributor mechanics.

Check tailpipe for individual exhaust puff.. trouble being it's hard if you dont know what normal is.. amazing the people who dont!

Check plugs.. any too rich or too lean?

 

Can I see a pic of your 5.7 V-10???

Sorry, I couldn't resist.