CArnuk
Higher voltage coils don't make an engine run BETTER. If the coil you replaced was a bad one the engine might have reverted to running NORMALLY...but if the coil you replaced was a good one it couldn't possibly run any better.
High voltage coils jump the gap in the plug at the same voltage as lower voltage coils... It is the nature of the beast.
Higher voltage coils are needed when the pressure they must discharge under is higher.. so high that a lower voltage coil cannot fire.
As long as the coil is working as designed, the coil that comes on an engine cannot be improved on! Unless of course other changes to the engine have raised the pressure at which the coil intends to discharge.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />