Amen.
Throwing lots of parts at a problem will bankrupt you, and not help the car...I know.
It is possible that even a cheap code reader or the "free read" at neighborhood auto parts store might tell you the problem.
But it might take VIDA/DiCe...
Could be any one of a plethora or items: a cracked vacuum hose, fouled PCV system, an intermittently failing coil, fouled plug, bad gas, stopped up fuel filter, one of many sundry sensors failing, plugged injector, etc., etc...
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