I can only help you a little bit here.
Any misfire in the engine is interpreted by the O2 sensor as a lean condition.
Therefore, the ECU would normally add more fuel to the equation.
Your HC readings are a DIRECT result of the misfire ( it only takes a very small misfire to elevate HC by 200 - 300 ppm ).
So, in my opinion you need to determine & rectify the exact cause of this misfire, as otherwise you're just chasing your tail with this.
