+1 ^^^
Your Buick had a problem with EGR system which was why removing it made it run better, lol.
EGR systems improve performance, when working, by allowing more aggressive spark timing when running 87 octane, cheap, gasoline.
Exhaust gas recirculation(EGR) was added to lower NOX emissions which spiked high when cylinders heated up under a load, adding exhaust gases lowers cylinder temps at that time so lowers NOX levels.
87 octane gasoline will self ignite as cylinder temps get high, so pinging/knocking is heard under load, knock sensors were installed on some engines, but on others the spark timing was just advanced so spark occurred before self ignition could, which reduces power.
But knock sensor or always advance spark timing still means less power
Which is why an engine setup/programmed for EGR system will run better with a working EGR system than without it.
Cat converters, that are working, don't effect performance one way or the other, when they start breaking apart inside then they block exhaust flow so do effect performance.
As adsm08 said your 1990 2.9l system is pretty basic, electronic spark, fuel injection and a computer to calculate air:fuel mix on the fly
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