Check/reseat injector plugs to make sure one wasn't locked in and is working itself out. Removed plugs and check appearance. I've found on some platinum plugs that the platinum wire will start to protrude out of the insulation and start closing the gap. If your plug wires are the traditional type with crimped ends they're probably not making any contact with the dsitributor hole posts. This creates an extra gap for the spark voltage to jump contributing to a weaker spark.