changeing frequency

Well, I have now made some small changes to an old power supply of mine. I
have an old ignition coil that im using now. I am able to change the
operating frequency of the power suppy from about 100Hz to about 10KHz. Is
there anything i can do or try with this????????There does seem to be a
frequency where my power supply is optimal and it wasnt at its previously
set frequency.
Also, if i have two of these igniton coils, how can i connect them up to
the same primary circuit if they separate power supplys????????????????
And one last question, If one coil delivers a high current and the other
delivers a high voltage and they are connected to the same primary circuit,
does that circuit get the best of both worlds ie high currnt and
voltage???? I  dont think it can!!??