Trying to elimenate pinholes(many) and blowholes(some)

Situation:
Through hole technology, 0.062 double side PCB
OA 20% solids flux, .905 spec gravity
Wave Temp - 500*F  Preheat top side temp of 190*F
Speed 4.5 FPM

Have tried baking 215*F for 2 hours
Have microsectioned board, copper in holes looks good

Believe some components could be contaminated, could this cause the
condition?
Looking for suggestions

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