Timing vs. Idle vs. Throttle Spacer WTH?

Hey all I’m absolutely lost. Had this truck for a couple months and have no clue how to get running right. 1988 C3500 5.7TBI. Bringing it home it died at every stop the SES light came on. Code 22.

Changed out the TPS, but realized as I removed it PO had installed wrong (tab was on wrong side of arm) reinstalled original TPS - code disappeared. Since then done: cap, rotor, plugs, wires, CTS, cleaned IAC and still runs like crap. Dies at every light.

Today I checked timing (properly with EST removed) and it was 8+ advanced. I set it 0 and now I can barely get it into gear before it dies.

Any suggestions? I don’t want to run advanced, hoping to be a daily driver and carry my TC for summer but so far can’t even get out of garage.

ALSO PO out a Throttle body spacer on it (no chip). Could this be the issue? Know nothing about them, can I simply remove without modification?

Thanks so much.

Check for vacuum leaks. Check your O2 sensor voltage; it should swing back and forth from .1 to .9 volts about seven times in ten seconds. If you can read data stream, check your temp sensor.

Also, check fuel pressure.

Thanks @Erik the Awful and @Dravec for the suggestions. Apologize for the duplicate post! Mods please remove.

The outer ring on the harmonic balancer can move and while not common happens more than people think. Just watched a power nation show where the engine on the dyno ran at something like 45 degrees advanced. They kept bumping the timing until it made max power. The engine doesn't lie so they were sure the balancer had slipped.

Ken