Plugs & wires are a good start. If the problem persist, you need to change the fuel filter and check the coil resistance. Coils should read on the primary side near 0.5-0.9 (ohms) & secondary side (k-ohm) 5.0-8.0.
I usually use an old spark plug gapped to .250 connected to the spark plug end of the ignition wire & grounded. While cranking the engine, observe the plug for spark. If you see a crisp blue spark, the ignition coil is working properly. If you only see a pale yellow spark, more than likely, you have a weak coil. I have seen quite a few coils that would pass the resistance test, however, not produce max voltage output.
