Do you have distributor or coil over plugs on your engine? I believe they changed to separate coils for each plugs around 95? If you have distributors on each bank I would check the inside for pitting on the rotor and cap. Have you checked if there are any codes? How is the idle?
How old are your spark plugs? Could be worthwhile to remove one and inspect. If you decide to change, buy non-resistor plugs, the ones specified in your owners manual.
In general, check all vacuum lines and connections. Check your alternator output. You should have at least 13,5V at idle with AC on. If not, your voltage regulator could be worn down. Very easy fix. What mileage are we talking about here?
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