The built-in light is just for emissions-related codes, there are several others the most important of which is the engine management. It won't necessarily trigger a CEL just because there's a code stored in the one that has the built-in light, only certain failures and occurance frequency/quantity will trip the CEL.

But it's up to you, if it only has a slight hesitation you might just find that new plugs and plug connectors / wires will make it run perfectly. Can also be a slight vacuum leak but that usually affects idle also.

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Gone to the dark side

- Jeff