1989 Trooper -- ignition timing off, does not advance

I am helping someone with a 1988 Isuzu Trooper (gasoline). I will not pass emissions test for the idling part of the test, and it seems to
have low power and feels like it "floods" when you first press on the gas to go, instead of the engine winding up smoothly.
The owner just finished replacing several different parts, including the EGR valve and O2 sensor, spark plugs and wires, mass air flow sensor, and it gives no error codes now. It runs a little better but not much.
I put a timing light on it and the timing appears to be way off, the mark is maybe 30 degrees to the passenger side as you look down at the crank. I did pull off and plug up the two vacuum tubes that you are supposed to.
The timing is so off that you can't twist the distributor enough to bring it to the correct spot. I even thought that I might have it on the wrong plug wire but I was on the No. 1.
I noticed that as the engine was reved, the timing stayed steady instead of moving as it would if the ignition timing advance was operational. I think that the problem is that the ignition timing is not advancing, and that a previous mechanic set it far in advance when tuning it "by ear" and got it barely running that way.
Does this make sense ?
What part controlls the ignition timing advance, that I can replace ?
Thanks in advance,
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