From what I am reading, it sounds like the engine is not getting fuel in the amount it needs (too lean). I would recommend checking your fuel filter for any obstruction or need of cleaning. If the fuel filter is directional, make certain that it is allowing the fuel to flow towards the engine. Directional filters that are put in backwards will retard fuel flow leading to a lean condition.
The exhaust deflector will require a minor tweak to the tuning as it changes the performance characteristics of the engine mildly.
If the filter checks okay, then I would try richening up your HSN about 1/4 turn from what it was before you added the filter and deflector.
The new glo-plug can also help, but it sounds to me more like you have a fuel flow issue.